Semiconductor-type laminated ceramic capacitor with a grain boundary-insulated structure

ABSTRACT

The present invention provides a semiconductor-type laminated ceramic capacitor with a grain boundary-insulated structure made of Sr.sub.(1-x) Ba x  TiO 3  as a main component, comprising the functions of a conventional capacitor which absorbs low voltage noises and high frequency noises, and a varistor when high voltage noises and electrostatic charges invade, wherein simultaneous sintering of the materials of ceramic capacitor together with the materials of inner electrodes was made possible in the manufacturing process. Besides a material to be made semiconductive is added to the main component of Sr.sub.(1-x) Ba x  TiO 3  with excess Ti, the materials of Mn-Si, which are converted to MnO 2  and SiO 2  in the sintering process, are also added to the main component. According to the manufacturing method of the present invention, calcination process of laminated raw sheets prevents troubles occurring in laminated ceramic capacitors with varistor function, comprising: breaks of electric connections in inner electrodes; de-lamination of ceramic sheet; cracks in ceramic sheet; decrease of sintering density; and non-uniformity in the texture of sintered body. It improves electric characteristics, i.e. capacitance, voltage non-linearity coefficient α and varistor voltage, and is reliable. The present invention provides two major advantages in the composition of materials and in the manufacturing process.

TECHNICAL FIELD

The present invention relates to a semiconductor-type laminated ceramiccapacitor with a grain boundary-insulated structure and a method forproducing the same, and more particularly to a ceramic capacitor whichabsorbs both low voltage noises and high frequency noises under thenormal operational conditions as a capacitor, works as a varistoragainst invading high voltage loads such as pulses and electrostaticcharges, thereby protecting built-in semiconductors and electronicequipment from being damaged by abnormal voltage loads such as noises,pulses and electrostatic charges arising from surrounding electronicequipment, wherein characteristics of said ceramic capacitor beingstable to temperature changes.

BACKGROUND ART

Recently, semiconductor elements such as IC and LSI are widely used inelectronic devices and equipment to realize multifunctional applicationsof the equipment and to make the equipment light, small and handy.However, the use of many semiconductor elements makes the electronicdevices less resistant to disturbance by electric noises. Theconventional method to protect the electronic devices from invadingelectric noises is to integrate by-pass capacitors such as filmcapacitor, laminated ceramic capacitor and semiconductor ceramiccapacitor into the power line of IC and LSI. These capacitors displayexcellent performances in absorbing low voltage noises and highfrequency noises. They are, however, so impotent to high voltage pulsesand electrostatic charges that malfunctionings of the equipment,break-down of semiconductors and/or capacitors themselves occurfrequently when the electronic equipment are invaded by high voltagepulses or electrostatic charges. Therefore, these technical problems inthe conventional capacitors should be improved.

A new type capacitor, which has sufficient resistance and excellentabsorbing ability to pulses as well as good noise absorbing ability andstability to temperature and frequency changes, was developed anddisclosed in Japanese Laid-Open Patent Publication No. 57-27001 andJapanese Laid-Open Patent Publication No. 57-35303 (corresponding toU.S. Pat. Nos. 4,519,942 and 4,541,974) etc., wherein a varistorfunction was added to a ceramic capacitor made of SrTiO₃ series ofceramic materials and the capacitor was defined as "a grain boundaryinsulated, semiconductor type ceramic capacitor having a varistorfunction" (hereinafter referred to as a ceramic capacitor with varistorfunction). This ceramic capacitor with varistor function works as avaristor when high voltage pulses and electrostatic charges invade it,and absorbs low voltage noises and high frequency noises as aconventional capacitor, thereby protecting the electronic equipment andbuilt-in semiconductors from abnormal high voltage noises, pulses andelectrostatic charges generated by surrounding electronic equipment anddevices, and providing wide application fields of the capacitor.

Since the electronic parts are made to be more sophisticated, lighter,smaller, and more handy, ceramic capacitors with varistor function arealso required to be smaller but higher in performance. The effectiveelectrode area of the conventional single-plate type ceramic capacitorwith varistor function will be, however, decreased when the capacitor isminiaturized, resulting in the reduction of electric capacitance andhence inferior reliability of the capacitor. A capacitor havinglaminated structure of the electrode is devised to solve theaforementioned problem, wherein the effective electrode area is expectedto be increased. However, the ceramic capacitor with varistor functionis conventionally manufactured by the process comprising a step coatingthe surface of SrTiO₃ type semiconductor element with oxides, followedby a thermal diffusion process to form an electric insulating layer inthe grain boundaries. It is recognized to be very difficult tomanufacture "a laminate type ceramic capacitor having varistor function"(hereinafter referred to as a laminated ceramic capacitor with varistorfunction) by sintering the material of the ceramic capacitorsimultaneously with the material of an inner electrode, thoughconventional laminated ceramic capacitors made of BaTiO₃ series ofmaterials are manufactured by this process.

As a method to overcome the problem of simultaneous formation of amaterial of laminated ceramic capacitor with varistor function bysintering the material of the ceramic capacitor together with thematerial of inner electrode, the following method for manufacturing alaminated ceramic capacitor with varistor function is developed andprovided, using methods as are disclosed in Japanese Laid-Open PatentPublication No. 54-53248 and Japanese Laid-Open Patent Publication No.54-53250, comprising the steps of: printing a pattern corresponding tothe inner electrode by using ceramic paste enriched in organic binder onthe surface of the ceramic substrate; forming a porous sheetcorresponding to the pattern of the inner electrode by sintering; andimpregnating the porous sheet with electrically conducting metals underthe appropriate pressure, or alternatively a step of forming a patternof inner electrodes by gilding or fusion method. These processes,however, involve many difficulties and they are yet far from practicalapplications.

Japanese Laid-Open Patent Publication No. 59-215701 provides a methodcomprising the manufacturing steps of: forming a raw sheet made ofceramic powder calcinated in the non-oxidizing atmosphere; printing apattern of the inner electrode by using an electric conductive pastemixed with a thermal diffusion material on the surface of the row sheet,said thermal diffusion material having the ability to form an electricinsulating layers in the grain boundaries; and sintering said raw sheetin the oxidizing atmosphere. Another method disclosed in JapaneseLaid-Open Patent Publication No. 63-219115 comprises the manufacturingsteps of: forming a raw sheet made of semiconductive ceramic powder as amain component, said main component being mixed with oxide to form aninsulating layer and/or diffusion material containing a glass material;laminating said raw sheets with a plurality of inner electrode sheetsmutually one by one; and sintering said laminated sheets in air or inthe oxidizing atmosphere. In the above-discussed two manufacturingmethods, however, sintering is performed at relatively low temperaturesof 1000-1200° C. Therefore, the capacitor elements thus formed are not aperfect sintered body of ceramic powder wherein grain boundaries arescarcely contacted with their faces. The ceramic capacitors obtainedentail the shortcomings comprising: relatively small electriccapacitance; small value of voltage non-linearity coefficient α which isa representative characteristics of a capacitor having varistorfunction; instability of varistor voltage; and inferior reliability as acapacitor. The manufacturing method disclosed in the latter invention,Japanese Laid-Open Patent Publication No. 63-219115, involves the stepof adding a glass material to the ceramic powder which entails a problemin that glassy phase deposits in the grain boundaries, whereby saidelectric characteristic tends to be poor and the capacitor element isnot recognized as reliable. The manufacturing process is considered tobe far from practical.

Concerning the laminated capacitors having varistor function, voltagenon-linear laminated capacitor elements made of ZnO, Fe₂ O₃ and TiO₂series of ceramic material have been provided in Japanese Laid-OpenPatent Publication No. 58-23921. Capacitance of the capacitor elementsof this type are, however, very small and they involve deficiencies thatthey display little effect to the electric noises with voltage of belowthe varistor region or to high frequency noises, while they haveexcellent ability to absorb pulses and electrostatic charges ofrelatively high voltage.

DISCLOSURE OF THE INVENTION

Although many attempts have been made and the technical results areprovided in the prior art concerning the compositions and manufacturingmethods of the various kinds of laminated ceramic capacitors withvaristor function, they involve deficiencies and shortcomings withregards to the manufacturing process itself or to the performances ofthe capacitor elements manufactured. None of them are considered to bepractical yet, and novelties in compositions and manufacturing methodsof the laminated ceramic capacitors with varistor function are expectedto be developed.

The present invention with respect to the above has an objective toprovide a semiconductor-type laminated ceramic capacitor with a grainboundary-insulated structure made of the materials of Sr.sub.(1-x)Ba_(x) TiO₃ type ceramics as a main component and a method for producingthe same, providing the functions of: a conventional capacitor to absorblow voltage noises and high frequency noises ; a varistor when highvoltage pulses and electrostatic charges invade the circuit; and acapacitor having the characteristics of being stable to temperaturevariations, wherein the capacitor element is manufactured bysimultaneous sintering of the materials of ceramic capacitor togetherwith the inner electrode materials.

The present invention, which overcomes the deficiencies and shortcomingsof the prior art, provides a semiconductor-type laminated ceramiccapacitor with a grain boundary-insulated structure comprising aplurality of inner electrodes on the surface of the grain boundaryinsulated, semiconductor type ceramic sheets, the terminal of each ofsaid inner electrodes being extended to one edge of the correspondingceramic sheet and said ceramic sheets being laminated so that saidterminals of said inner electrodes come to the corresponding oppositeedges of said ceramic sheets alternatively one by one; and outerelectrodes electrically connected to said terminals of inner electrodesat the edge of said grain boundary insulated, semiconductor type ceramicsheets, wherein said ceramic sheets comprise a material of thecomposition of Sr.sub.(1-x) Ba_(x) TiO₃ containing excess Ti to makefinal molecular ratio of Ti to Sr.sub.(1-x) Ba_(x) in the range of0.95≦Sr.sub.(1-x) Ba_(x) /Ti<1.00 (where x is in the range of 0<x≦0.3);at least one or more kinds of the compounds selected from Nb₂ O₅, Ta₂O₅, V₂ O₅ , W₂ O₅, Dy₂ O₃, Nd₂ O₃, Y₂ O₃, La₂ O₃ or CeO₂ are added tothe ceramic material to make their relative molar content in the rangefrom 0.05 to 2.0%; and Mn and Si are also included in the ceramicmaterial to the amount of their combined relative molar content,converting into MnO₂ and SiO₂ respectively, in the range of 0.2 to 5.0mol %.

Generally speaking, ceramic material of the composition of Sr.sub.(1-x)Ba_(x) TiO₃ is made semiconductive by a forced reduction process or,after adding an accelerating agent to make the material semiconductive,by a sintering process in the reducing atmosphere. The process to makethe material semiconductive, however, may remain incomplete according tothe nature of the agent used. When the amount of Sr.sub.(1-x) Ba_(x) orTi is made slightly in excess out of the stoichiometric ratio ofSr.sub.(1-x) Ba_(x) TiO₃, lattice defect in the crystal of the ceramicswill increase, thereby accelerating the material to be semiconductive.In addition, the ceramic material is made semiconductive advantageouslyby adding Nb₂ O₅, Ta₂ O₅, V₂ O₅, W₂ O₅, Dy₂ O₃, Nd₂ O₃, Y₂ O₃, La₂ O₃ orCeO₂ (hereinafter referred to as first components) since these compoundscontrol the atomic valency.

Next, Mn and Si (hereinafter referred to as second components) are theessential compounds to form a laminated structure and absence of one ofthe two compounds will result in the incomplete formation of thelamellar structure. As mentioned above, manufacturing of laminatedceramic capacitors with varistor function was considered to be difficultin the prior art. The first reason depends on the fact that the materialfor the ceramic capacitor with varistor function such as SrTiO₃ seriesof ceramics displays a different nature and behavior with the materialof inner electrode during the sintering and re-oxidation processes. Theformer materials require a reducing atmosphere in the sintering processwhile the latter materials made of metals expand in volume by occludinghydrogen gas in the reducing atmosphere. Furthermore, the lattermaterial is oxidized into metal oxide and tends to block re-oxidation ofthe former material during the re-oxidation process in the air.

Formation of a ceramic capacitor element with varistor function by usingthe former material, which is the second reason why the process isdifficult, involves a process of surface diffusion comprising the stepsof: making the material semiconductive by sintering in the reducingatmosphere; covering the surface of the ceramic sheets with metal oxideswith high electric resistance (i.e. MnO₂, CuO₂, Bi₂ O₃, Co₂ O₃) followedby re-oxidation in the air; and insulating grain boundaries by selectivediffusion of the metal oxides. However, in the structure of thecapacitor element laminated by the ceramic plate and inner electrodematerial mutually one by one, diffusion of metal oxides into grainboundaries is technically difficult.

The inventors of the present invention discovered the following factsthrough their studies.

First, a ceramic capacitor with varistor function was readilymanufactured by adding the second components as well as the firstcomponents into the ceramic material of Sr.sub.(1-x) Ba_(x) TiO₃ withexcess Ti, and by sintering the material in the reducing atmospherefollowed by re-oxidation process. Spreading of metal oxide paste withhigh electric resistance over the surface of the ceramic plates wasfound to be needless to form insulating grain boundaries. Theexperimental facts are interpreted as follows; the second componentsadded, together with excess Ti, forms a liquid phase comprising of Mn,Si and Ti ternary oxide system at relatively low temperatures duringsintering process. The liquid phase enhances sintering of grains whilethe oxides melt and segregate in the grain boundaries. Re-oxidation ofthe capacitor element, in the boundaries of which a liquid phasecomprising of Mn, Si and Ti ternary oxide system is formed in the air,completes the formation of an insulating metal oxide film comprisingsegregated ternary oxides of Mn, Si and Ti in the grain boundaries,thereby readily producing a ceramic capacitor with varistor functionhaving the structure of a grain boundary insulation layer. Excess Ti wasfound to prevent oxidation of inner electrode as well as diffusion ofmetal oxides into the inner electrode. For this reason the ceramicmaterial of Sr.sub.(1-x) Ba_(x) TiO₃ with excess Ti was used in thepresent invention.

Second, the material of Sr.sub.(1-x) Ba_(x) TiO₃, with excess Ti, towhich the second component was added, was made semiconductive bysintering in the nitrogen atmosphere as well as in the reducingatmosphere. The finding can be partly interpreted by the same reason asis described in the discussions of the first experiment, in that thematerial is made liquid phase at relatively low temperature. The Mnadded not only forms a liquid phase but also works as an atomic valencecontrol agent. In working as an atomic valence control agent, the ionicvalence of Mn ion is +2 or +4 and its electronic state is unstable andliable to be excited, thereby increasing the sinterability. This is thereason the ceramic material is readily made semiconductive through thesintering process in the nitrogen atmosphere by adding Mn ion as asecond component.

Third, the raw materials formed into the laminated capacitor sheets werecalcinated in the air before being subjected to the sintering process.This treatment prevented the product, laminated ceramic capacitor withvaristor function, from breaking electric connections in the innerelectrodes, de-lamination of the ceramic sheets, cracking in the ceramicsheets, decrease in sintering density and nonuniformity in the sinteredbody etc. Furthermore, electric characteristics and reliability inperformance of the capacitor such as capacitance, voltage non-linearitycoefficient α and varistor voltage was also largely improved.

According to the present invention, with respect to the above, alaminated ceramic capacitor with varistor function, comprising themanufacturing steps of sintering the material of ceramic capacitor withvaristor function together with materials of inner electrodesimultaneously, can be readily manufactured.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is an exploded perspective view to explain the examples of thepresent invention, showing laminated raw sheets and the pattern of theinner electrode paste printed on said raw sheet. FIG. 2 is a partiallycutaway view of the laminated ceramic capacitor with varistor functionobtained from the examples of the present invention. FIG. 3 is a flowchart showing the process to manufacture the laminated ceramic capacitorwith varistor function to explain the examples of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Details of the present invention will be described hereinafter withreference to the examples.

Example 1

Powders of TiO₂ were added to the powder material of Sr₀.8 Ba₀.2 TiO₃ ofmean particle size of 0.5 μm or less and purity of 98% or more,adjusting the molar ratio of Sr.sub.(1-x) Ba_(x) /Ti (hereinafterreferred to as A/B ratio). First component, Nb₂ O₅, and secondcomponents, MnO₂ and SiO₂ (the relative molar content of the twocompounds are made equal, respectively), were weighed and mixed to thematerial described above, as are shown in Tables 1-15. The mixed powderwas ground and mixed in a wet state by using a ball mill and, afterdrying, the ground powder was subjected to a calcination process byheating at 600-1200° C. in the air. The calcinated powder was groundagain to make a mean particle size of 0.5 μm or less, to provide thepowder for the starting material of a laminated ceramic capacitor withvaristor function. The finely powdered starting material was dispersedin an organic solvent together with an organic binder such as butyralresin compound to form a slurry. The slurry was next formed into a rawsheet with its thickness of about 50 μm by using the method of Dr.Blade, and the sheet was cut into a predetermined size.

A pattern of inner electrode paste 2 containing Pd was printed by ascreen printing technique corresponding to the predetermined size, as isshown in FIG. 1, on the raw sheet 1 formed by the above-describedmethod. As is apparent from FIG. 1, inner electrode pastes 2 are notprinted on the uppermost and lowermost part of the raw sheet 1a in thelaminated capacitor material. The pattern of inner electrode paste 2 onthe intermediate part of the laminated raw sheet 1 reaches to the oneedge of the sheet, and the edges are distributed alternatively one byone to the opposite(different) directions in the laminates. The rawsheets 1a were disposed on the uppermost and lowermost parts and rawsheets 1 printed with the above inner electrode pastes thereon werelaminated therebetween, a plurality of this sheet pairs were pressed andcompacted with a heat treatment. The pressed sheets were then calcinatedand degreased by heating at 600-1250° C. in the air. The calcinatedsheets were next subjected to sintering by heating at 1200-1350° C. in areducing atmosphere, followed by re-oxidation by heating at 900-1250° C.in the air.

As shown in FIG. 2, the outer electrode paste containing Ag was paintedon the edges of the sheets where terminals of inner electrodes 2a wereexposed alternatively and the silver paste was baked by heating at 800°C. for 15 minutes in the air, thereby completing a ceramic capacitor 4with varistor function, comprising a plurality of inner electrode 2a onthe surface of the grain boundary insulated semiconductor type ceramicsheets, the terminals of said inner electrodes 2a reaching to each ofopposite edge of the sheet alternatively one by one; and outerelectrodes 3 at opposite edges of the semiconductor type ceramic sheets,said outer electrodes being connected electrically to the terminals ofsaid inner electrodes 2a exposed to the edges of the sheetsalternatively.

Size of the laminated ceramic capacitor of this example, abbreviated asType 5.5, is 5.70 mm in width, 5.00 mm in length and 2.00 mm inthickness. The capacitor is composed of 10 effective sheets on which apattern of inner electrodes is printed, and non-effective sheets onwhich the pattern of inner electrode is not printed, wherein both typesof sheets are laminated alternatively, one by one. FIG. 3 shows amanufacturing process flow sheet of the present invention.

According to the laminated ceramic capacitor with varistor function thusmanufactured, electrical characteristics such as capacitance, tan δ,varistor voltage, voltage non-linearity coefficient α, equivalent seriesresistance (ESR), capacitance-temperature rate of change and temperaturecoefficient of varistor voltage are listed in Tables 1-15. Theexperimental conditions for sample preparation were; 1200° C., 2 hoursfor calcination and degreasing in the air; 1300° C., 2 hours forsintering in the reducing atmosphere of N₂ :H₂₌ 99:1; and 1100° C., 1hour for re-oxidation.

Each electrical characteristic was obtained by the followingexperimental conditions.

* Capacitance was measured at 1.0V, 1.0 KHz.

* Varistor voltage V₀.1mA was measured at 0.1 mA.

* Voltage non-linearity coefficient α was calculated from the values ofvaristor voltage measured at 0.1 mA and 1.0 mA, respectively, using thefollowing equation

    α=1/log (V.sub.1.0mA /V.sub.0.1mA)

* Equivalent series resistance (ESR) is defined as resistance atresonance frequency measured at 1.0V.

* Capacitance-temperature rate of change (ΔC/C) was calculated from thevalues measured at -25° C. and 85° C., respectively.

* Temperature coefficient of varistor voltage (ΔV/V) was calculated fromthe values measured at 25° C. and 50° C., respectively.

                                      TABLE 1                                     __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.95)                                  Nb.sub.2 O.sub.5 ; 0.05 mol %                                                 The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ)                                                                       (%) (%/°C.)                              __________________________________________________________________________    *1   0.0     0.3 1.3                                                                              531 1  2.0k                                                                             -12.4                                                                             -10.5                                       *2   0.1     0.8 1.2                                                                              119 2  1.2k                                                                             -9.1                                                                              -5.3                                        3    0.2     12  1.5                                                                              21  3  391                                                                              -5.3                                                                              -1.8                                        4    0.5     90  1.5                                                                              13  4  93 -4.5                                                                              -1.5                                        5    1.0     357 1.7                                                                               7  8  47 -4.1                                                                              -1.3                                        6    2.0     476 1.7                                                                               4  11 35 -4.0                                                                              -1.5                                        7    3.0     341 1.8                                                                               7  8  50 -3.2                                                                              -1.5                                        8    4.0     102 1.7                                                                              11  6  148                                                                              -4.6                                                                              -1.4                                        9    5.0     12  1.2                                                                              19  3  371                                                                              -6.4                                                                              -1.6                                        *10  6.0     0.8 1.9                                                                              121 2  1.5k                                                                             -11.3                                                                             -6.1                                        __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 2                                     __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.95)                                  Nb.sub.2 O.sub.5 ; 0.1 mol %                                                  The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ                                                                        (%) (%/°C.)                              __________________________________________________________________________    *11  0.0     0.3 1.5                                                                              511 1  2.0k                                                                             -11.2                                                                             -11.5                                       *12  0.1     0.8 1.3                                                                              119 2  1.2k                                                                             -8.7                                                                              -7.3                                        13   0.2     12  1.3                                                                              19  3  367                                                                              -5.4                                                                              -1.5                                        14   0.5     91  1.5                                                                              14  4  93 -4.1                                                                              -1.5                                        15   1.0     366 1.2                                                                               7  8  46 -5.5                                                                              -1.4                                        16   2.0     479 1.4                                                                               4  11 37 -4.2                                                                              -1.3                                        17   3.0     340 1.4                                                                               8  8  51 -3.5                                                                              -1.4                                        18   4.0     105 1.5                                                                              11  6  80 -3.5                                                                              -1.3                                        19   5.0     12  1.5                                                                              22  3  359                                                                              - 5.4                                                                             -1.7                                        *20  6.0     0.8 1.9                                                                              127 2  1.5k                                                                             -8.7                                                                              -7.6                                        __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 3                                     __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.95)                                  Nb.sub.2 O.sub.5 ; 0.5 mol %                                                  The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ)                                                                       (%) (%/°C.)                              __________________________________________________________________________    *21  0.0     0.3 1.4                                                                              451 1  2.0k                                                                             -10.6                                                                             -8.5                                        *22  0.1     3   1.7                                                                              32  3  667                                                                              -8.4                                                                              -3.1                                        23   0.2     14  1.8                                                                              19  4  304                                                                              -5.0                                                                              -1.4                                        24   0.5     99  1.5                                                                              12  4  72 -4.1                                                                              -1.2                                        25   1.0     383 1.5                                                                               6  8  43 -4.2                                                                              -1.3                                        26   2.0     496 1.5                                                                               4  11 36 -3.3                                                                              -1.2                                        27   3.0     357 1.4                                                                               7  8  48 -3.1                                                                              -1.5                                        28   4.0     128 1.3                                                                               9  6  68 -4.2                                                                              -1.3                                        29   5.0     15  1.4                                                                              20  4  301                                                                              - 6.5                                                                             -1.6                                        *30  6.0     3   1.9                                                                              31  3  682                                                                              -10.2                                                                             -4.7                                        __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 4                                     __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.95)                                  Nb.sub.2 O.sub.5 ; 1.0 mol %                                                  The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ)                                                                  ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ                                                                        (%) (%/°C.)                              __________________________________________________________________________    *31  0.0     0.3 1.5                                                                              421 1  2.0k                                                                             -9.9                                                                              -7.9                                        *32  0.1     4   1.3                                                                              23  3  534                                                                              -8.1                                                                              -2.8                                        33   0.2     22  1.5                                                                              11  5  172                                                                              -4.2                                                                              -1.2                                        34   0.5     128 1.4                                                                               9  5  67 -3.4                                                                              -1.4                                        35   1.0     394 1.1                                                                               6  9  43 -4.0                                                                              -1.3                                        36   2.0     524 1.5                                                                               4  13 31 -3.2                                                                              -1.1                                        37   3.0     382 1.3                                                                               6  8  43 -3.5                                                                              -1.7                                        38   4.0     136 1.3                                                                               8  7  62 -4.1                                                                              -1.3                                        39   5.0     25  1.2                                                                              11  5  165                                                                              - 6.5                                                                             -1.5                                        *40  6.0     4   1.3                                                                              24  3  532                                                                              -9.6                                                                              -4.3                                        __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 5                                     __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.95)                                  Nb.sub.2 O.sub.5 ; 2.0 mol %                                                  The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ)                                                                       (%) (%/°C.)                              __________________________________________________________________________    *41  0.0     0.3 1.6                                                                              513 1  2.0k                                                                             -11.1                                                                             -11.5                                       *42  0.1     0.8 1.3                                                                              115 2  1.2k                                                                             -8.5                                                                              -7.2                                        43   0.2     12  1.3                                                                               21 3  363                                                                              -5.3                                                                              -1.6                                        44   0.5     92  1.4                                                                               13 5  91 -4.2                                                                              -1.4                                        45   1.0     371 1.5                                                                               7  7  44 -5.3                                                                              -1.2                                        46   2.0     490 1.4                                                                               4  10 34 -4.4                                                                              -1.3                                        47   3.0     345 1.3                                                                               7  7  48 -3.6                                                                              -1.4                                        48   4.0     111 1.5                                                                               11 5  80 -3.5                                                                              -1.3                                        49   5.0     12  1.3                                                                               21 3  357                                                                              -5.6                                                                              -1.6                                        *50  6.0     0.8 1.9                                                                              114 2  1.5k                                                                             -8.9                                                                              -7.7                                        __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 6                                     __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  Nb.sub.2 O.sub.5 ; 0.05 mol %                                                 The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ)                                                                       (%) (%/°C.)                              __________________________________________________________________________    *51  0.0     0.3 1.3                                                                              451 1  2.0k                                                                             -9.9                                                                              -8.3                                        *52  0.1     1   1.4                                                                              90  2  1.0k                                                                             -7.3                                                                              -3.1                                        53   0.2     15  1.5                                                                              16  4  278                                                                              -4.2                                                                              -1.3                                        54   0.5     124 1.3                                                                              10  6  71 -4.4                                                                              -1.4                                        55   1.0     476 1.2                                                                               5  9  35 -4.1                                                                              -1.1                                        56   2.0     631 1.4                                                                               4  13 28 -3.1                                                                              -1.3                                        57   3.0     456 1.5                                                                               5  9  39 -3.2                                                                              -1.5                                        58   4.0     150 1.4                                                                               9  7  62 -4.2                                                                              -1.3                                        59   5.0     17  1.5                                                                              16  4  248                                                                              -5.4                                                                              -1.5                                        *60  6.0     1   1.7                                                                              81  2  1.0k                                                                             -9.3                                                                              -5.1                                        __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 7                                     __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  Nb.sub.2 O.sub.5 ; 0.1 mol %                                                  The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ)                                                                       (%) (%/°C.)                              __________________________________________________________________________    *61  0.0     0.4 1.2                                                                              402 1  2.0k                                                                             -10.2                                                                             -7.1                                        *62  0.1     1   1.3                                                                              91  2  1.0k                                                                             -7.2                                                                              -3.0                                        63   0.2     15  1.4                                                                              16  4  270                                                                              -4.0                                                                              -1.2                                        64   0.5     121 1.4                                                                              10  6  72 -4.1                                                                              -1.6                                        65   1.0     486 1.3                                                                               5  10 35 -4.1                                                                              -1.1                                        66   2.0     641 1.5                                                                               4  13 28 -3.3                                                                              -1.4                                        67   3.0     451 1.3                                                                               5  10 37 -3.0                                                                              -1.4                                        68   4.0     141 1.6                                                                               9  7  60 -3.7                                                                              -1.3                                        69   5.0     15  1.4                                                                              17  4  271                                                                              -4.8                                                                              -1.5                                        *70  6.0     1   1.8                                                                              85  1  1.0k                                                                             -8.9                                                                              -5.1                                        __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 8                                     __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  Nb.sub.2 O.sub.5 ; 0.5 mol %                                                  The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ)                                                                       (%) (%/°C.)                              __________________________________________________________________________    *71  0.0     0.4 1.2                                                                              402 1  2.0k                                                                             -9.9                                                                              -6.1                                        *72  0.1     4   1.3                                                                              23  3  501                                                                              -6.8                                                                              -4.3                                        73   0.2     19  1.3                                                                              14  5  228                                                                              -4.1                                                                              -1.2                                        74   0.5     151 1.3                                                                               8  6  54 -3.8                                                                              -1.6                                        75   1.0     519 1.3                                                                               5  11 35 -3.8                                                                              -1.2                                        76   2.0     663 1.4                                                                               4  14 27 -3.1                                                                              -1.2                                        77   3.0     481 1.4                                                                               5  10 35 -2.9                                                                              -1.2                                        78   4.0     180 1.5                                                                               6  8  51 -3.4                                                                              -1.2                                        79   5.0     19  1.3                                                                              14  5  228                                                                              -4.7                                                                              -1.3                                        *80  6.0     4   1.9                                                                              22  3  501                                                                              -8.8                                                                              -5.5                                        __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 9                                     __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  Nb.sub.2 O.sub.5 ; 1.0 mol %                                                  The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ)                                                                       (%) (%/°C.)                              __________________________________________________________________________    *81  0.0     0.4 1.3                                                                              405 1  2.0k                                                                             -8.8                                                                              -6.1                                        *82  0.1     5   1.4                                                                              19  4  399                                                                              -7.1                                                                              -3.1                                        83   0.2     36  1.3                                                                              9   6  125                                                                              -3.5                                                                              -1.2                                        84   0.5     170 1.3                                                                              7   7  51 -3.4                                                                              -1.3                                        85   1.0     530 1.3                                                                              5   12 31 -3.5                                                                              -1.1                                        86   2.0     706 1.5                                                                              4   17 24 -3.5                                                                              -1.2                                        87   3.0     507 1.3                                                                              5   10 34 -3.0                                                                              -1.2                                        88   4.0     184 1.4                                                                              6   9  47 -3.4                                                                              -1.2                                        89   5.0     39  1.3                                                                              8   6  126                                                                              -4.1                                                                              - 1.2                                       *90  6.0     5   1.9                                                                              20  4  392                                                                              -8.6                                                                              -5.9                                        __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 10                                    __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  Nb.sub.2 O.sub.5 ; 2.0 mol %                                                  The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ)                                                                       (%) (%/°C.)                              __________________________________________________________________________    *91  0.0     0.3 1.5                                                                              453 1  2.0k                                                                             -10.5                                                                             -7.8                                        *92  0.1     1   1.3                                                                              92  2  1.0k                                                                             -7.4                                                                              -4.1                                        93   0.2     15  1.3                                                                              17  4  272                                                                              -4.4                                                                              -1.3                                        94   0.5     122 1.4                                                                              19  6  68 -4.0                                                                              -1.4                                        95   1.0     490 1.3                                                                               5  9  35 -4.3                                                                              -1.4                                        96   2.0     653 1.5                                                                               4  13 24 -3.8                                                                              -1.3                                        97   3.0     459 1.4                                                                               5  9  36 -3.4                                                                              -1.5                                        98   4.0     143 1.3                                                                               9  7  60 -4.1                                                                              -1.3                                        99   5.0     18  1.4                                                                              17  4  269                                                                              -5.8                                                                              -1.5                                        *100 6.0     1   1.8                                                                              91  2  1.0k                                                                             -9.9                                                                              -5.7                                        __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 11                                    __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.99)                                  Nb.sub.2 O.sub.5 ; 0.05 mol %                                                 The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ)                                                                       (%) (%/°C.)                              __________________________________________________________________________    *101 0.0     0.3 1.5                                                                              499 1  2.0k                                                                             -10.6                                                                             -10.1                                       *102 0.1     0.6 1.3                                                                              151 1  1.5k                                                                             -9.4                                                                              -1.5                                        103  0.2     9   1.4                                                                              21  2  474                                                                              -5.2                                                                              -1.3                                        104  0.5     68  1.5                                                                              12  3  122                                                                              -4.5                                                                              -1.3                                        105  1.0     275 1.4                                                                               8  5  64 -4.4                                                                              -1.4                                        106  2.0     362 1.4                                                                               5  7  48 -4.6                                                                              -1.5                                        107  3.0     262 1.4                                                                               8  5  64 -4.8                                                                              -1.3                                        108  4.0     78  1.5                                                                              11  4  111                                                                              -5.5                                                                              -1.3                                        109  5.0     9   1.4                                                                              22  2  472                                                                              -6.5                                                                              -1.5                                        *110 6.0     0.6 1.8                                                                              151 1  1.5k                                                                             -8.9                                                                              -10.0                                       __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 12                                    __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.99)                                  Nb.sub.2 O.sub.5 ; 0.1 mol %                                                  The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ)                                                                       (%) (%/°C.)                              __________________________________________________________________________    *111 0.0     0.3 1.5                                                                              500 1  2.0k                                                                             -10.5                                                                             -9.9                                        *112 0.1     0.6 1.4                                                                              144 1  1.5k                                                                             -9.0                                                                              -1.4                                        113  0.2     9   1.4                                                                              21  2  473                                                                              -5.1                                                                              -1.4                                        114  0.5     70  1.4                                                                              15  4  134                                                                              -4.4                                                                              -1.5                                        115  1.0     277 1.3                                                                               9  6   63                                                                              -4.3                                                                              -1.4                                        116  2.0     364 1.4                                                                               5  7   44                                                                              -4.3                                                                              -1.4                                        117  3.0     262 1.4                                                                               9  6   65                                                                              -4.9                                                                              -1.4                                        118  4.0     80  1.5                                                                              11  4  108                                                                              -5.2                                                                              -1.3                                        119  5.0     9   1.3                                                                              21  2  470                                                                              -5.8                                                                              -1.4                                        *120 6.0     0.6 1.9                                                                              139 1  1.5k                                                                             -10.1                                                                             -9.6                                        __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 13                                    __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.99)                                  Nb.sub.2 O.sub.5 ; 0.5 mol %                                                  The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ)                                                                       (%) (%/°C.)                              __________________________________________________________________________    *121 0.0     0.3 1.4                                                                              450 1  2.0k                                                                             -9.5                                                                              -8.5                                        *122 0.1     2   1.4                                                                              35  2  871                                                                              -5.7                                                                              -1.4                                        123  0.2     10  1.3                                                                              21  3  389                                                                              -4.8                                                                              -1.3                                        124  0.5     87  1.3                                                                              11  4  97 -4.1                                                                              -1.3                                        125  1.0     294 1.3                                                                               9  6  57 -4.0                                                                              -1.3                                        126  2.0     376 1.3                                                                               5  8  46 -4.2                                                                              -1.4                                        127  3.0     269 1.3                                                                               9  6  63 -3.8                                                                              -1.3                                        128  4.0     57  1.4                                                                              10  5  88 -4.2                                                                              -1.4                                        129  5.0     10  1.3                                                                              21  3  387                                                                              -5.5                                                                              -1.4                                        *130 6.0     2   1.9                                                                              34  2  877                                                                              -9.5                                                                              -9.4                                        __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 14                                    __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.99)                                  Nb.sub.2 O.sub.5 ; 1.0 mol %                                                  The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ)                                                                       (%) (%/°C.)                              __________________________________________________________________________    *131 0.0     0.3 1.4                                                                              451 1  2.0k                                                                             -9.3                                                                              -9.5                                        *132 0.1     3   1.4                                                                              32  2  702                                                                              -4.8                                                                              -1.3                                        133  0.2     19  1.3                                                                              15  4  217                                                                              -4.5                                                                              -1.3                                        134  0.5     97  1.3                                                                              12  4  89 -4.1                                                                              -1.4                                        135  1.0     301 1.2                                                                               8  7  55 -3.9                                                                              -1.3                                        136  2.0     400 1.2                                                                               5  10 41 -3.8                                                                              -1.3                                        137  3.0     292 1.2                                                                               9  6  59 -3.7                                                                              -1.3                                        138  4.0     107 1.3                                                                              10  5  80 -4.1                                                                              -1.2                                        139  5.0     19  1.3                                                                              14  4  217                                                                              -4.7                                                                              - 1.3                                       *140 6.0     3   1.9                                                                              30  2  708                                                                              -7.1                                                                              -9.4                                        __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 15                                    __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.99)                                  Nb.sub.2 O.sub.5 ; 2.0 mol %                                                  The relative molar contents of MnO.sub.2 and SiO.sub.2 are made equal.        Sample                                                                             MnO.sub.2 + SiO.sub.2                                                                 C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                  Number                                                                             (mol %) (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ)                                                                       (%) (%/°C.)                              __________________________________________________________________________    *141 0.0     0.3 1.6                                                                              501 1  2.0k                                                                             -10.2                                                                             -9.6                                        *142 0.1     0.6 1.4                                                                              142 1  1.5k                                                                             -9.5                                                                              -1.5                                        143  0.2     9   1.4                                                                              19  2  474                                                                              -5.3                                                                              -1.3                                        144  0.5     70  1.4                                                                              13  4  120                                                                              -4.5                                                                              -1.3                                        145  1.0     282 1.4                                                                               9  6  61 -4.3                                                                              -1.4                                        146  2.0     372 1.4                                                                               5  7  47 -4.3                                                                              -1.4                                        147  3.0     262 1.4                                                                               8  6  64 -4.9                                                                              -1.3                                        148  4.0     82  1.5                                                                              11  4  109                                                                              -5.6                                                                              -1.3                                        149  5.0     9   1.5                                                                              21  2  472                                                                              - 6.1                                                                             -1.6                                        *150 6.0     0.6 1.6                                                                              142 1  1.5k                                                                             -9.8                                                                              -9.9                                        __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

Next, the data listed in Tables 1-15 show the effect of A/B ratio ofSr.sub.(1-x) Ba_(x) TiO₃ and the effect of the amount of added secondcomponent, MnO₂ and SiO₂, to the characteristics of the capacitor.

The samples marked by the symbol * in the tables are listed forcomparison and they are not included in the range of claims in thepresent invention. The sintered bodies marked by the symbol * possesssmall capacitance, small value of voltage non-linearity coefficient α,which is a representative characteristic of varistors, and a large valueof equivalent series resistance (ESR). The capacitor having theabove-discussed characteristics cannot display the performances both ofa normal capacitor, which absorbs low voltage noises and high frequencynoises, and of a varistor which absorbs high voltage pulses andelectrostatic charges, at the same time. The capacitor has relativelylarge capacitance-temperature rate of variation and varistor voltagetemperature coefficient, whereby making reliability and electriccharacteristics of the capacitor liable to be affected by temperaturechange. Therefore, these samples are not suited for the use of a ceramiccapacitor with varistor function which protects electronic devices andequipment from being damaged by abnormal voltage such as noises, pulsesand electrostatic charge generated by surrounding electronic equipment.Other samples which are not marked in the tables, possess largecapacitance, large value of voltage non-linearity coefficient α andsmall equivalent series resistance (ESR). A capacitor with thesecharacteristics displays the performances both of a normal capacitor,which absorbs low voltage noises and high frequency noises, and of avaristor which absorbs high voltage pulses and electrostatic charges.The capacitor has relatively small capacitance-temperature rate ofvariation and varistor voltage temperature coefficient, thereby makingreliability and electric characteristics of the capacitor hardly liableto be affected by temperature change. Therefore, these samples are wellsuited for the use of a ceramic capacitor with varistor function whichprotects electronic devices and equipment from being damaged by abnormalvoltage such as noises, pulses and electrostatic charge generated bysurrounding electronic equipment.

In the present invention, A/B ratio is controlled because, when A/Bratio is greater than 1.00, the amount of Sr.sub.(1-x) Ba_(x) will be inexcess relative to the amount of Ti, thereby preventing the formation ofthe liquid phase composed of Mn, Si and Ti ternary oxide system. Grainboundary insulated structure of the ceramics is difficult to be formedwith above-mentioned composition and, moreover, oxidation and diffusionof the materials of the inner electrode occur, resulting in poorelectric characteristics and reliability. On the other hand, when A/Bratio is less than 0.95, the sintered body obtained will be porous andsintering density decreases. Powder materials of its mean particle sizeof 0.5 μm or less was used for the starting material of laminatedceramic capacitor with varistor function because, if the powder of meanparticle size of more than 0.5 μm or is used, the particles tend tocoagulate in the slurry, thereby making the surface of raw sheets formedby using such non-uniform slurry gritty and not smooth. Sinteringdensity and packing density of the sintered body obtained are small andthe sintered body is difficult to make semiconductive, thereby electriccharacteristics of the ceramic capacitor tends to be unstable.

Next, total amount of the second component added, MnO₂ and SiO₂, arealso controlled because, when the combined relative molar content of thesecond component is less than 0.2%, the effect of the added material ishardly reflected in the formation of the liquid phase composed of Mn, Siand Ti ternary oxide system. Grain boundary insulated structure of theceramics is difficult to form, thereby sintering density of the ceramiccapacitor obtained is decreased and electric characteristics tend to bepoor. On the other hand, when the relative molar content of the secondcomponent added exceeds 5.0%, the amount of metal oxides with highelectric resistance segregating in the grain boundaries increases andelectric characteristics of the ceramic capacitor also degrades.

The process of calcination and degreasing by heating the raw sheet at600-1250° C. in the air is most important in the method of formation ofa laminated ceramic capacitor with varistor function in the presentinvention. Most of electric characteristics and reliability of theceramic capacitor with varistor function manufactured are determinedduring this process. The purposes of the process are to enhance adhesiveforce between the material of ceramic capacitor with varistor functionand material of the inner electrode, and to adjust sintering density,uniformity in the texture of sintered body, and mean grain size of thecrystal particles in the grain boundary insulated semiconductor typeceramics of the laminated ceramic capacitor with varistor function. Therate of temperature increase was adjusted to 200° C./hr or less in thedegreasing and calcination process because the slower the temperatureincrease was, the more desirable results were obtained after thedegreasing and calcination process.

The temperature for degreasing and calcination in the air is limitedbetween 600 and 1250° C. When the temperature is lower than 600° C., theprocess is not effective enough and when the temperature for calcinationexceeds 1250° C., electric characteristics and reliability of thecapacitor will be largely decreased because of the following reasons;

(1) The ceramic capacitor with varistor function is sintered instead ofbeing calcinated by heating at this high temperature range. When thecapacitor sintered previously in the air is subjected to sintering inthe reducing atmosphere or in the nitrogen atmosphere, the sintered bodyshrinks rapidly and suffers by concentrated stress, thereby producingde-lamination and cracks in the laminated ceramic capacitor withvaristor function.

(2) Oxidation of Ni as well as sintering of ceramic capacitor withvaristor function will proceed at the same time when Ni is used as amaterial for inner electrode. The sintered body reacts with Ni followedby the diffusion of Ni, resulting in breaking of inner electrode,de-lamination and formation of cracks in the laminated ceramic capacitorwith varistor function.

(3) Sintering in the liquid phase of Mn, Si and Ti ternary oxide systemproceed rapidly under the sintering condition at high temperature over1250° C. and growth of grains is accelerated, thereby largely decreasingsintering density and packing density.

(4) The sintered body treated by above-mentioned manner is difficult tomake semiconductive by the sintering process in reducing or nitrogenatmosphere afterward.

The laminated ceramic capacitor with varistor function thus manufacturedhas larger capacitance and displays much better temperature andfrequency characteristics than the capacitor disclosed in aforementionedJapanese Laid-Open Patent Publication No. 58-23921. The ceramiccapacitor in the present invention is manufactured by laminating ceramiccapacitor materials with varistor function which possesses bothfunctions of a normal capacitor which absorbs noises, and of a varistorwhich absorbs pulses and electrostatic charge, while the above-mentionedcapacitor in the prior art is simply made of piled varistor materialwhich shows prominent absorbing ability for surge current. The laminatedceramic capacitor with varistor function in the present invention isdistinct from that in the prior art in both its functions and uses.

Example 2

It was found from Example 1 that the amount of the added secondcomponent, the combined amount of MnO₂ and SiO₂, should be in the rangeof relative molar content of 0.2-5.0%. A laminated ceramic capacitorwith varistor function was manufactured by using a similar method asdescribed in Example 1, except that molar ratio of MnO₂ and SiO₂, thesecond components, was changed variously. A / B ratio in the perovskitestructure of SrO₀.8 Ba₀.2 TiO₃ was fixed to 0.97 and relative molarcontent of Nb₂ O₅ added as first component was fixed to 1.0%. Theresults are listed in Table 16.

                                      TABLE 16                                    __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  Nb.sub.2 O.sub.5 ; 1.0 mol %                                                  Sample                                                                             MnO.sub.2                                                                          SiO.sub.2                                                                          C   tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                Number                                                                             (mol %)                                                                            (mol %)                                                                            (nF)                                                                              (%)                                                                              (V) α                                                                          (mΩ)                                                                       (%) (%/°C.)                            __________________________________________________________________________    *151 2.0  0.0  0.3 2.5                                                                              452 1  2.0k                                                                             -10.2                                                                             -7.2                                      152  1.8  0.2  10  1.3                                                                              14  4  400                                                                              -5.4                                                                              -1.5                                      153  1.5  0.5  733 1.4                                                                              4   18 22 -3.5                                                                              -1.2                                      154  1.0  1.0  706 1.5                                                                              4   17 24 -3.5                                                                              -1.2                                      155  0.5  1.5  184 1.3                                                                              4   7  50 -4.6                                                                              -1.5                                      156  0.2  1.8  9   1.8                                                                              18  4  400                                                                              -6.5                                                                              -1.7                                      157  0.0  2.0  0.3 1.9                                                                              452 1  2.0k                                                                             -10.5                                                                             -8.3                                      __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

As is apparent from the experimental results in Table 16, both Mn and Siwhich convert into MnO₂ and SiO₂ in the sintering process are requiredfor manufacturing the laminated ceramic capacitor with varistor functionand an absence of one of the two compounds does not result in theformation of the same. The liquid phase composed of Mn, Si and Titernary oxide system is only allowed to form in the presence of theabove-mentioned two compounds. A capacitor element having grain boundaryinsulated structure is formed readily when Mn, Si and Ti ternary oxidesystem segregates among grain boundaries and is made insulating byre-oxidization.

MnO₂ is preferably added in slight excess to obtain a capacitor ofdesirable electric characteristics such as capacitance, voltagenon-linearity factor α and ESR.

Example 3

A laminated ceramic capacitor was manufactured according to the methodsdescribed in Examples 1 and 2, except that the added amounts of firstcomponents which serve as a valency controlling agent were changedvariously, i.e. Nb₂ O₅, Ta₂ O₅, V₂ O₅, W₂ O₅, Dy₂ O₃, Nd₂ O₃, Y₂ O₃, La₂O₃ or CeO₂. A/B ratio of Sr₀.8 Ba₀.2 TiO₃ was fixed to 0.97 whilecombined relative molar content of second components was fixed to 1.0%for MnO₂ and 1.0% for SiO₂, the total amount of which was fixed to 2.0%.The results are described in Tables 17-25.

                  TABLE 17                                                        ______________________________________                                        Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample                                                                              Ta.sub.2 O.sub.5                         ΔV/V                     Num-  (mol    C      tan δ                                                                        V.sub.0.1mΛ                                                                      ESR  ΔC/C                                                                          (%/                            ber   %)      (nF)   (%)  (V)   α                                                                           (mΩ)                                                                         (%)   °C.)                    ______________________________________                                        *158  0.02    0.3    2.0  450    1  2.0k -8.9  -7.5                           159   0.05    626    1.5  4     13  27   -3.8  -1.5                           160   0.1     644    1.4  4     13  27   -3.5  -1.5                           161   0.5     672    1.4  4     14  26   -3.4  -1.3                           162   1.0     697    1.4  4     17  25   -3.6  -1.3                           163   2.0     605    1.5  4     13  27   -3.7  -1.3                           *164  3.0      4     2.1  24     3  260  -10.8 -7.5                           ______________________________________                                         Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                  TABLE 18                                                        ______________________________________                                        Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample                                                                              V.sub.2 O.sub.5                          ΔV/V                     Num-  (mol    C      tan δ                                                                        V.sub.0.1mΛ                                                                      ESR  ΔC/C                                                                          (%/                            ber   %)      (nF)   (%)  (V)   α                                                                           (mΩ)                                                                         (%)   °C.)                    ______________________________________                                        *165  0.02    0.3    2.0  450    1  2.0k -8.2  -7.4                           166   0.05    597    1.5  4     12  30   -3.9  -1.5                           167   0.1     617    1.5  4     13  29   -3.7  -1.5                           168   0.5     648    1.3  4     14  26   -3.8  -1.4                           169   1.0     671    1.4  4     15  27   -3.7  -1.3                           170   2.0     544    1.5  4     12  29   -3.8  -1.3                           *171  3.0      4     2.1  25     3  264  -11.2 -8.6                           ______________________________________                                         Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                  TABLE 19                                                        ______________________________________                                        Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample                                                                              W.sub.2 O.sub.5                          ΔV/V                     Num-  (mol    C      tan δ                                                                        V.sub.0.1mΛ                                                                      ESR  ΔC/C                                                                          (%/                            ber   %)      (nF)   (%)  (V)   α                                                                           (mΩ)                                                                         (%)   °C.)                    ______________________________________                                        *172  0.02    0.3    2.0  450    1  2.0k -8.1  -7.4                           173   0.05    595    1.5  4     13  29   -3.7  -1.5                           174   0.1     615    1.4  4     13  28   -3.6  -1.5                           175   0.5     638    1.4  4     13  27   -3.5  -1.4                           176   1.0     665    1.5  4     14  27   -3.6  -1.3                           177   2.0     563    1.5  4     13  27   -3.6  -1.4                           *178  3.0      4     2.1  24     3  260  -10.7 -8.6                           ______________________________________                                         Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                  TABLE 20                                                        ______________________________________                                        Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample                                                                              Dy.sub.2 O.sub.3                         ΔV/V                     Num-  (mol    C      tan δ                                                                        V.sub.0.1mΛ                                                                      ESR  ΔC/C                                                                          (%/                            ber   %)      (nF)   (%)  (V)   α                                                                           (mΩ)                                                                         (%)   °C.)                    ______________________________________                                        *179  0.02    0.3    2.0  450    1  2.0k -8.9  -7.5                           180   0.05    602    1.4  4     12  30   -3.5  -1.6                           181   0.1     617    1.5  4     13  29   -3.7  -1.5                           182   0.5     646    1.4  4     14  27   -3.7  -1.4                           183   1.0     663    1.4  4     15  27   -3.7  -1.4                           184   2.0     563    1.5  4     12  30   -3.5  -1.5                           *185  3.0      4     2.1  25     3  265  -11.0 -8.6                           ______________________________________                                         Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                  TABLE 21                                                        ______________________________________                                        Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample                                                                              Nd.sub.2 O.sub.3                         ΔV/V                     Num-  (mol    C      tan δ                                                                        V.sub.0.1mΛ                                                                      ESR  ΔC/C                                                                          (%/                            ber   %)      (nF)   (%)  (V)   α                                                                           (mΩ)                                                                         (%)   °C.)                    ______________________________________                                        *186  0.02    0.3    2.0  450    1  2.0k -8.5  -7.5                           187   0.05    609    1.4  4     12  28   -3.9  -1.5                           188   0.1     624    1.5  4     13  28   -3.6  -1.4                           189   0.5     651    1.3  4     14  25   -3.6  -1.4                           190   1.0     677    1.4  4     16  26   -3.6  -1.3                           191   2.0     561    1.5  4     12  29   -3.8  -1.3                           *192  3.0      4     2.0  25     3  262  -11.1 -6.7                           ______________________________________                                         Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                  TABLE 22                                                        ______________________________________                                        Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample                                                                              Y.sub.2 O.sub.3                          ΔV/V                     Num-  (mol    C      tan δ                                                                        V.sub.0.1mΛ                                                                      ESR  ΔC/C                                                                          (%/                            ber   %)      (nF)   (%)  (V)   α                                                                           (mΩ)                                                                         (%)   °C.)                    ______________________________________                                        *193  0.02    0.3    2.5  450    1  2.0k -8.6  -8.5                           194   0.05    575    1.5  5     11  33   -4.0  -1.5                           195   0.1     590    1.6  4     12  31   -3.9  -1.4                           196   0.5     614    1.3  4     13  26   -3.6  -1.3                           197   1.0     621    1.5  4     14  27   -3.6  -1.4                           198   2.0     561    1.5  5     10  35   -3.5  -1.4                           *199  3.0      4     2.2  26     3  265  -11.1 -7.9                           ______________________________________                                         Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                  TABLE 23                                                        ______________________________________                                        Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample                                                                              La.sub.2 O.sub.3                         ΔV/V                     Num-  (mol    C      tan δ                                                                        V.sub.0.1mΛ                                                                      ESR  ΔC/C                                                                          (%/                            ber   %)      (nF)   (%)  (V)   α                                                                           (mΩ)                                                                         (%)   °C.)                    ______________________________________                                        *200  0.02    0.3    2.0  450    1  2.0k  -9.81                                                                              -7.2                           201   0.05    581    1.4  5     12  30   -3.8  -1.5                           202   0.1     593    1.5  4     12  29   -3.7  -1.4                           203   0.5     617    1.3  4     13  26   -3.5  -1.4                           204   1.0     622    1.5  4     14  27   -3.5  -1.3                           205   2.0     563    1.6  5     10  31   -4.0  -1.4                           *206  3.0      4     2.1  25     3  255  -11.1 -6.7                           ______________________________________                                         Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                  TABLE 24                                                        ______________________________________                                        Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample                                                                              CeO.sub.2                                ΔV/V                     Num-  (mol    C      tan δ                                                                        V.sub.0.1mΛ                                                                      ESR  ΔC/C                                                                          (%/                            ber   %)      (nF)   (%)  (V)   α                                                                           (mΩ)                                                                         (%)   °C.)                    ______________________________________                                        *207  0.02    0.3    2.0  450    1  2.0k -10.1 -8.5                           208   0.05    580    1.4  5     12  29   -3.7  -1.4                           209   0.1     592    1.4  4     12  28   -3.6  -1.4                           210   0.5     615    1.4  4     13  26   -3.5  -1.4                           211   1.0     621    1.5  4     14  27   -3.5  -1.3                           212   2.0     561    1.5  5     10  30   -3.5  -1.3                           *213  3.0      4     2.2  25     3  260  -11.1 -8.4                           ______________________________________                                         Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

                                      TABLE 25                                    __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample                                                                             First Components                                                                       C  tan δ                                                                      V.sub.0.1mΛ                                                                  ESR                                                                              ΔC/C                                                                        ΔV/V                                   Number                                                                             (mol %)  (nF)                                                                             (%)                                                                              (V) α                                                                         (mΩ)                                                                       (%) (%/°C.)                               __________________________________________________________________________    214  Nb.sub.2 O.sub.5                                                                   0.5 716                                                                              1.1                                                                              4   18                                                                              23 -3.5                                                                              -1.2                                              Ta.sub.2 O.sub.5                                                                   0.5                                                                 215  Nb.sub.2 O.sub.5                                                                   0.5 683                                                                              1.4                                                                              4   16                                                                              25 -3.4                                                                              -1.2                                              V.sub.2 O.sub.5                                                                    0.5                                                                 216  Nb.sub.2 O.sub.5                                                                   0.5 681                                                                              1.3                                                                              4   16                                                                              25 -3.5                                                                              -1.3                                              W.sub.2 O.sub.5                                                                    0.5                                                                 217  Nb.sub.2 O.sub.5                                                                   0.5 655                                                                              1.3                                                                              4   14                                                                              28 -3.5                                                                              -1.3                                              Dy.sub.2 O.sub.3                                                                   0.5                                                                 218  Nb.sub.2 O.sub.5                                                                   0.5 646                                                                              1.4                                                                              4   13                                                                              28 -3.6                                                                              -1.3                                              Nd.sub.2 O.sub.3                                                                   0.5                                                                 219  Nb.sub.2 O.sub.5                                                                   0.5 530                                                                              1.7                                                                              6   10                                                                              33 -3.5                                                                              -1.4                                              Y.sub.2 O.sub.3                                                                    0.5                                                                 220  Nb.sub.2 O.sub.5                                                                   0.5 541                                                                              1.6                                                                              6   10                                                                              33 -3.6                                                                              -1.4                                              La.sub.2 O.sub.3                                                                   0.5                                                                 221  Nb.sub.2 O.sub.5                                                                   0.5 536                                                                              1.7                                                                              6   10                                                                              33 -3.5                                                                              -1.4                                              CeO.sub.2                                                                          0.5                                                                 __________________________________________________________________________

As is apparent from the results described in Tables 17-25, the amountsof the first components added are controlled because, when the relativemolar contents of the first components are less than 0.05%, the effectsof the additives are not enough to make the material semiconductive.When combined relative molar contents of the first components exceed2.0%, the material is depressed so as to be semiconductive, therebypreventing the capacitor from having predetermined electriccharacteristics and decreasing sintering density.

The addition of Nb₂ O₅ or Ta₂ O₅ as first component seemed to result inbetter electric characteristics of the capacitor than the cases when V₂O₅, W₂ O₅, Dy₂ O₅, Nd₂ O₃, Y₂ O₃, La₂ O₃ or CeO₂ was added.

The effects of mixed composition of first components to the electriccharacteristics of the capacitor were studied in several cases. Theaddition of two kinds or more of the first component to the ceramicmaterial displayed slight appreciable effect to the electriccharacteristics of the capacitor compared to the cases when onecomponent was added to the material, as shown in Table 25. The additionof Nb₂ O₅ and Ta₂ O₅, however, seemed to be more effective inmanufacturing a capacitor of better electric characteristics than theaddition of other components. As the sample No. 214 shows, simultaneousaddition of Nb₂ O₅ and Ta₂ O₅ resulted in better electriccharacteristics.

When mean particle size of the starting material was larger more than0.5 μm, the addition of first components tended to be not effective,therefore it was confirmed that mean particle size of the startingmaterial should be 0.5 μm or less.

Example 4

In the aforementioned examples Sr₀.8 Ba₀.2 TiO₃ was used as Sr.sub.(1-x)Ba_(x) TiO₃ (where 0<x≦0.3). A laminated ceramic capacitor with varistorfunction was manufactured by a using similar method described inExamples 1 to 3, except the number of x was changed. A/B ratio was fixedto 0.97 while relative molar contents of first components, 0.5% for Nb₂O₅ and Ta₂ O₅, respectively, and those of second components, 1.0% forMnO₂ and SiO₂, respectively, were also fixed, the total amount of whichwas fixed to 2.0%. The results are listed in Table 26.

                                      TABLE 26                                    __________________________________________________________________________    Sr.sub.(1-x) Ba.sub.x TiO.sub.3 (A/B = 0.97)                                  Mb.sub.2 O.sub.5 ; 0.5 mol %, Ta.sub.2 O.sub.5 ; 0.5 mol %                    MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample                                                                             Sr.sub.(1-x) Ba.sub.x TiO                                                             C  tan δ                                                                      V.sub.0.1mΛ                                                                   ESR                                                                              ΔC/C                                                                        ΔV/V                                   Number                                                                             (mol %) (nF)                                                                             (%)                                                                              (V)  α                                                                         (mΩ)                                                                       (%) (%/°C.)                               __________________________________________________________________________    222  Sr.sub.0.99 Ba.sub.0.1 TiO.sub.3                                                      421                                                                              1.0                                                                              4    18                                                                              23 -3.5                                                                              -1.2                                         223  Sr.sub.0.95 Ba.sub.0.05 TiO.sub.3                                                     501                                                                              1.0                                                                              4    18                                                                              23 -3.7                                                                              -1.2                                         224  Sr.sub.0.90 Ba.sub.0.10 TiO.sub.3                                                     595                                                                              1.1                                                                              4    18                                                                              23 -3.6                                                                              -1.2                                         225  Sr.sub.0.80 Ba.sub.0.20 TiO.sub.3                                                     716                                                                              1.1                                                                              4    18                                                                              23 -3.5                                                                              -1.2                                         226  Sr.sub.0.70 Ba.sub.0.30 TiO.sub.3                                                     817                                                                              1.5                                                                              4    18                                                                              23 -5.5                                                                              -1.8                                         *227 Sr.sub.0.60 Ba.sub.0.40 TiO.sub.3                                                     880                                                                              2.0                                                                              3    17                                                                              22 -10.9                                                                             -9.3                                         __________________________________________________________________________     Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

As is apparent from the results described in Table 26, the reason therange of x was defined is that Curie point of Sr.sub.(1-x) Ba_(x) TiO₃appears when x exceeds 0.3 and capacitance-temperature rate of changeand varistor voltage temperature rate of change becomes larger and thecapacitor characteristics and varistor characteristics become unstable,the temperature thereby decreases reliability and performance. Inaddition, as x exceeds 0.3 and the ratio of Ba increases, the structureof the semiconductor ceramic capacitor thus obtained will change fromthe grain boundary-insulated structure to the surface re-oxidationstructure.

Example 5

In the aforementioned examples Pd was used as a material of the innerelectrode. A laminated ceramic capacitor with varistor function wasmanufactured by using a similar method to that described in Examples 1to 4, except that Au, Pt, Rh or Ni was used as a material of the innerelectrode. The ratio of A / B of Sr₀.8 Ba₀.2 TiO₃ was fixed to 0.97,while relative molar contents of first components, 0.5% for Nb₂ O₅ andTa₂ O₅, respectively, and those of second components, 1.0% for MnO₂ andSiO₂, respectively, were also fixed. The results are listed in Table 27.

                                      TABLE 27                                    __________________________________________________________________________    Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  Nb.sub.2 O.sub.5 ; 0.5 mol %, Ta.sub.2 O.sub.5 ; 0.5 mol %                    MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample       C  tan δ                                                                      V.sub.0.1mΛ                                                                  ESR                                                                              ΔC/C                                                                        ΔV/V                                    Number                                                                             Inner Electrode                                                                       (nF)                                                                             (%)                                                                              (V) α                                                                         (mΩ)                                                                       (%) (%/°C.)                                __________________________________________________________________________    228  Pd      716                                                                              1.1                                                                              4   18                                                                              23 -3.5                                                                              -1.2                                          229  Ni      766                                                                              1.9                                                                              4   18                                                                              30 -3.6                                                                              -1.6                                          230  Pd--Ni  734                                                                              1.7                                                                              4   14                                                                              24 -3.5                                                                              -1.3                                          231  Au      527                                                                              1.8                                                                              7   10                                                                              34 -3.9                                                                              -1.5                                          232  Pt      541                                                                              1.8                                                                              6   10                                                                              34 -3.8                                                                              -1.7                                          237  Rh      540                                                                              1.8                                                                              6   10                                                                              33 -3.9                                                                              -1.8                                          234  Pt--Rh  524                                                                              1.8                                                                              7   10                                                                              35 -3.9                                                                              -1.9                                          __________________________________________________________________________

As described in Table 27, it was confirmed that at least one or morekinds of metals of Au, Pt, Rh, Pd and Ni, or alloys or compositionsthereof, could be used for the material of the inner electrode, each ofthem having an identical effect as electrode material. When Ni is usedfor inner electrode material, compositions of Pd to Ni or the use ofSr.sub.(1-x) Ba_(x) TiO₃ with slight excess in Ti is recommended sinceNi is prone to be oxidized at relatively low temperature.

It was also confirmed that compositions of metals other than thosedescribed in the examples of the present invention could be usedadvantageously for the material of the inner electrode.

In the examples of the present invention, powders of TiO₂ are added tothe powder material of Sr.sub.(1-x) Ba_(x) TiO₃ to prepare Sr.sub.(1-x)Ba_(x) TiO₃ with excess Ti. Needless to say, however, carbonate,hydroxide of Ti or organic Ti compounds are also used advantageously forthe preparation of the same starting material.

In the examples of the present invention, Sr.sub.(1-x) Ba_(x) TiO₃ wasused as powder material. Needless to say, however, powder material ofSr.sub.(1-x) Ba_(x) TiO₃ prepared from the materials of SrO or SrCO₃ andBaO or BaCO₃ and TiO₂ is used successfully for manufacturing thecapacitor elements of identical characteristics.

As for MnO₂ and SiO₂ as a second component, carbonates or hydroxides ofthem are also effective for the preparation of the starting material.With respect to Mn, however, use of MnCO₃ was confirmed to be moreappropriate for manufacturing a capacitor element with stablecharacteristic and good mass productivity, because the particle sizedistribution of the compound is fine and uniform, and the compound isreadily pyrolyzed.

In the aforementioned examples, the sintering process was performed in areducing atmosphere of the composition of N₂ :H₂₌ 99:1. When H₂concentration in the atmosphere is increased, the following phenomenaare observed with regard to both the material of the inner electrode andthe material of the ceramic capacitor with varistor function;

(1) Electrode material is expanded by occluding H₂ gas.

(2) The material of the ceramic capacitor with varistor function isfacilitated to be semiconductive.

These phenomena entail the problems in laminated ceramic capacitor withvaristor function with respect to electric and mechanicalcharacteristics, comprising; breaking of electrical connections in theinner electrodes, de-lamination of the ceramic sheet, occurrence ofcracking in ceramic sheets and incomplete re-oxidation of ceramicmaterials. Consequently, when sintering is performed in an atmosphere inwhich H₂ concentration is increased, it is preferable for manufacturinga ceramic capacitor with desirable characteristics that sinteringtemperature range is made a little lower (1200-1300° C). On thecontrary, ceramic capacitor with varistor function is rather difficultto be semiconductive when it is sintered in N₂ atmosphere or in anatmosphere containing a smaller amount of H₂ gas. Therefore, thematerial is preferably sintered in a little higher temperature range(1300° C.-1450° C.). H₂ concentration relative to N₂ is most preferablyin the range of 99.5:0.5≦N₂ :H₂≦ 95.0: 5.0.

In the above-mentioned examples, mixed powder was calcinated in the air.Calcination process performed in N₂ atmosphere was confirmed, however,to be advantageous also.

With regard to the re-oxidation process, the material was re-oxidized ata predetermined temperature of 1100° C. in the above examples. Thetemperature range of 900-1250° C. is also advantageous for re-oxidationto manufacture a capacitor element with desirable characteristics. Whenre-oxidation is performed at the highest temperature of 1200° C. ormore, the duration of high temperature should be as short as possible.Otherwise, not only the materials in grain boundaries but also crystalgrains are oxidized and made insulating. When Ni is used for the innerelectrode material, prolonged heating at 1200° C. or more forre-oxidation will oxidize metallic Ni itself. Therefore, duration ofheating time at higher temperature for re-oxidation should be carefullykept as short as possible.

Ag was used for the material of the outer electrode in the examplesdescribed above. However, Pd, Ni, Cu and Zn were confirmed to be usedadvantageously for the same purpose. The material for the outerelectrode comprises at least one or more kinds of Pd, Ag, Ni, Cu and Zn,and alloys or compositions of them. When Pd or Ag is used for thematerial of outer electrode, an appreciable polarization is observed inthe varistor voltage because the metals are rather difficult to makeohmic contact with the capacitor element. However, the basiccharacteristics of the capacitor is not influenced at all bypolarization.

Mean particle size of the powder material of laminated ceramic capacitorwith varistor function manufactured by the method disclosed in the aboveexamples was approximately in the range of 2.0-3.0 μm. When calcinationis achieved by heating at 1300° C. or higher in the air, sintering ofliquid phase of Mn, Si and Ti ternary oxide system is accelerated andconsequently growth of grains is enhanced, thereby increasing mean grainsize up to twice or more. Increased mean grain size entails manyproblems comprising; decreasing in sintering density and packingdensity, decreasing in voltage non-linearity coefficient α, decreasingin equivalent series resistance (ESR) and dispersing in electriccharacteristics. The ceramic capacitor thus manufactured would be poorin electric characteristics and reliability, thereby making thecapacitor inappropriate to practical uses.

The capacitor element thus obtained comprises the advantages of; largecapacitance and voltage non-linearity coefficient α, small varistorvoltage and equivalent series resistance (ESR), and excellenttemperature and frequency characteristics, whereby absorbing low voltagenoises and high frequency noises as a function of an ordinary capacitor,absorbing high voltage pulses and electrostatic charges as a function ofa varistor, and responding quickly to invading abnormal voltages such asnoises, pulses and electrostatic charges. The capacitor is expected toreplace various uses of conventional capacitors such as film, laminatedceramic and semiconductor capacitors. Moreover, laminated ceramiccapacitors with varistor function of the present invention are smallerin size and larger in capacitance compared to conventional single platetype ceramic capacitor with varistor function, thereby a wide range ofapplications such as mounting parts in circuit cards is also expected.

In the aforementioned examples, laminated ceramic capacitor withvaristor function composed of grain boundary insulated, semiconductortype ceramic was described, said ceramic being composed of Sr.sub.(1-x)Ba_(x) TiO₃ in which excess Ti (where 0<x≦0.3) is contained so as toadjust the molar ratio of Sr.sub.(1-x) Ba_(x) to Ti in the range of0.95≦Sr.sub.(1-x) Ba_(x) /Ti<1.00, wherein first component such as Nb₂O₅ and/or Ta₂ O₅ are added in relative molar content of 0.05-2.0%, andcombined second components of Mn and Si, converting in molecular weightof MnO₂ and SiO₂ respectively, are added in relative molar content of0.2-5.0%. According to the present invention, further improvements incharacteristics of the capacitor elements made of grain boundaryinsulated, semiconductor type ceramic are expected, when third andfourth components are added to the ceramic material.

Detailed examples are described hereinafter.

Example 6

Na₂ SiO₃ is added as third component in this example and the effectswill be described in further detail with reference to the example.

A laminated ceramic capacitor with varistor function was manufactured byusing similar methods as described in Examples 1 to 4, except that theamount of the added third component, Na₂ SiO₃, was variously adjustedand changed. A/B ratio of Sr₀.8 Ba₀.2 Ba₀.2 TiO₃ was fixed to 0.97; therelative molar content of first components was fixed to 0.5% for Nb₂ O₅and Ta₂ O₅, respectively, while those of combined second components wasfixed to 1.0% for MnO₂ and SiO₂, respectively. The results are listed inTable 28.

                  TABLE 28                                                        ______________________________________                                        Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  Nb.sub.2 O.sub.5 ; 0.5 mol %, Ta.sub.2 O.sub.5 ; 0.5 mol %                    MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample                                    ΔC/                                                                          ΔV/V                     Num-  Na.sub.2 SiO.sub.3                                                                     C      tan δ                                                                        V.sub.0.1mΛ                                                                      ESR  C    (%/                            ber   (mol %)  (nF)   (%)  (V)   α                                                                           (mΩ)                                                                         (%)  °C.)                    ______________________________________                                        *235  0.02     716    1.0  4     18  23   -3.5 -1.2                           236   0.05     715    1.0  4     18  24   -2.3 -0.5                           237   0.1      714    1.0  4     18  24   -2.4 -0.5                           238   0.5      711    1.0  4     18  24   -2.3 -0.5                           239   1.0      659    1.2  4     16  26   -2.4 -0.4                           240   2.0      621    1.5  5     15  30   -2.4 -0.5                           *241  3.0      341    3.0  8      8  48   -5.6 -1.8                           ______________________________________                                         Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

As described in Table 28, capacitance-temperature rate of variation andvaristor voltage temperature coefficient are improved by adding thethird component, Na₂ SiO₃. Na₂ SiO₃ works as a carrier to diffuse liquidphase of Mn, Si and Ti ternary oxide system uniformly in the grainboundaries, thereby forming distinct interfaces among the semiconductorcrystal region and a high resistance grain boundary region. When therelative molar content of third component added, Na₂ SiO₃, is less than0.05%, the effects of the additive is not clear and few improvements incapacitance-temperature rate of variation and varistor voltagetemperature coefficient are observed. When relative molar content ofthird component is over 2.0%, Na₂ SiO₃ which serves as a carrier will bein excess in grain boundaries, thereby decreasing capacitance andvoltage non-linearity coefficient α, increasing equivalent seriesresistance (ESR), decreasing sintering density and degrading mechanicalstrength.

A mixture of Na₂ O and SiO₂ can also be used as a third componentinstead of Na₂ SiO₃. Since Na₂ O is a very unstable compound anddecomposes readily during the sintering process, it is liable to scatteror diffuse into the atmosphere, leaving few Na atoms in the manufacturedsintered body. Moreover, it was confirmed that migration of partiallyionized Na⁺¹ ion under the load of high temperature and high voltageentails degradation of capacitor characteristics. The effects of addedNa ion is provided advantageously by adding the ion in the form of acompound with SiO₂.

It was confirmed that Na ion should be added to the material in the formof a compound of Na₂ SiO₃.

Example 7

Next, an example where NaAlO₂ is added as a third component will bedescribed. A laminated ceramic capacitor with varistor function wasmanufactured by using similar methods described in Examples 1 to 4,except that the amount of added third component, NaAlO₂, was variouslyadjusted and changed as described in Example 6. A/B ratio of Sr₀.8 Ba₀.2Ba₀.2 TiO₃ was fixed to 0.97; the relative content of first componentswas fixed to 0.5% for Nb₂ O₅ and Ta₂ O₅, respectively, while those ofcombined second components were fixed to 1.0% for MnO₂ and SiO₂,respectively. The results are listed in Table 29.

                  TABLE 29                                                        ______________________________________                                        Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  Nb.sub.2 O.sub.5 ; 0.5 mol %, Ta.sub.2 O.sub.5 ; 0.5 mol %                    MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample                                    ΔC/                                                                          ΔV/V                     Num-  Na.sub.2 AlO.sub.2                                                                     C      tan δ                                                                        V.sub.0.1mΛ                                                                      ESR  C    (%/                            ber   (mol %)  (nF)   (%)  (V)   α                                                                           (mΩ)                                                                         (%)  °C.)                    ______________________________________                                        *242  0.02     338    1.2  4     17  24   -3.1 -1.0                           243   0.05     639    1.2  4     19  23   -2.5 -0.6                           244   0.2      640    1.2  4     19  23   -2.5 -0.6                           245   1.0      640    1.2  4     19  23   -2.5 -0.6                           246   2.0      640    1.2  4     19  23   -2.5 -0.6                           247   4.0      636    1.7  4     19  23   -2.6 -0.6                           *248  5.0      307    3.7  8      8  38   -4.2 -2.0                           ______________________________________                                         Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

As described in Table 29, the first advantage of adding the thirdcomponent, NaAlO₂, to the ceramic material is, just like the addition ofNa₂ SiO₃ described in Example 6, in that it improves thecapacitance-temperature rate of change and varistor voltage temperaturecoefficient. Na atoms in added NaAlO₃ work as carriers to diffuse liquidphase of Mn, Si and Ti ternary oxide system homogeneously into grainboundaries, thereby forming distinct interfaces among semiconductivecrystal grains and grain boundaries of high electric resistance.

Second, voltage non-linearity coefficient α increases and equivalentseries resistance (ESR) decreases by adding NaAlO₂, because Al atoms inNaAlO₂ are solubilized in a solid state into the crystal lattice,thereby decreasing electric resistance of crystal grains. When relativemolar content of added NaAlO₂ is less than 0.05%, characteristics of thecapacitor are not influenced desirably by the additive; giving noimprovements in capacitance-temperature rate of change and varistortemperature coefficient, nor increasing voltage non-linearitycoefficient α, and not decreasing equivalent series resistance (ESR). Onthe other hand, when relative molar content of the additive exceeds4.0%, which means it exceeds the saturated solubility in the crystallattice, excess NaAlO₂ segregates in the grain boundaries, therebyincreasing electric resistance of the grain boundaries and hencedecreasing capacitance and voltage non-linearity coefficient α rapidlyand decreasing mechanical strength of the capacitor.

A mixture of Na₂ O and Al₂ O₃ can also be used as the third componentinstead of NaAlO₂. Since Na₂ O is a very unstable compound anddecomposes readily during the sintering process, it is liable to scatteror diffuse into the atmosphere, leaving few Na atoms in the manufacturedsintered body. Moreover, it was confirmed that migration of partiallyionized Na⁺¹ ion under the load of high temperature and high voltageentails degradation of capacitor characteristics. The effects of addedNa ion is provided advantageously by adding the ion in the form of acompound of NaAlO₂.

It was confirmed that Na ion should be added to the material in the formof a compound of NaAlO₂.

Example 8

An example where Li₂ SiO₃ is added as a third component will bedescribed. A laminated ceramic capacitor with varistor function wasmanufactured by using similar methods described in Examples 1 to 4,except that the amount of the added third component, Li₂ SiO₃, wasadjusted and changed variously as is described in Examples 6 and 7. A/Bratio of Sr₀.8 Ba₀.2 Ba₀.2 TiO₃ was fixed to 0.97; the relative contentof the first components was fixed to 0.5% for Nb₂ O₅ and Ta₂ O₅,respectively, while those of combined second components were fixed to1.0% for MnO₂ and SiO₂, respectively. The results are listed in Table30.

                  TABLE 30                                                        ______________________________________                                        Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  Nb.sub.2 O.sub.5 ; 0.5 mol %, Ta.sub.2 O.sub.5 ; 0.5 mol %                    MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample                                    ΔC/                                                                          ΔV/V                     Num-  Li.sub.2 SiO.sub.3                                                                     C      tan δ                                                                        V.sub.0.1mΛ                                                                      ESR  C    (%/                            ber   (mol %)  (nF)   (%)  (V)   α                                                                           (mΩ)                                                                         (%)  °C.)                    ______________________________________                                        *249  0.02     709    1.4  4     18  29   -3.9 -2.0                           250   0.05     703    1.4  4     18  30   -2.6 -1.2                           251   0.1      704    1.4  4     18  30   -2.7 -1.2                           252   0.5      702    1.4  4     18  30   -2.7 -1.0                           253   1.0      650    1.6  4     16  32   -2.7 -0.9                           254   0.2      617    1.8  5     15  32   -2.7 -1.2                           *255  3.0      337    3.4  8      8  52   -6.9 -2.4                           ______________________________________                                         Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

As described in Table 30, by adding the third component, Li₂ SiO₃, justlike Examples 6 and 7, capacitance-temperature rate of change andvaristor voltage temperature coefficient are improved. Added Li₂ SiO₃works as carriers to diffuse the liquid phase of Mn, Si and Ti ternaryoxide system homogeneously into grain boundaries, thereby formingdistinct interfaces among semiconductive crystal grains and grainboundaries of high electric resistance. When relative molar content ofadded Li₂ SiO₃ is less than 0.05%, characteristics of the capacitor arenot influenced desirably by the additive, giving no improvements incapacitance-temperature rate of change and varistor temperaturecoefficient. On the other hand, when relative molar content of theadditive exceeds 2.0%, the amount of carrier Li₂ SiO₃ increases, therebydecreasing capacitance and voltage non-linearity coefficient α,increasing equivalent series resistance (ESR), and decreasing sinteringdensity and mechanical strength of the capacitor.

A mixture of Li₂ O and SiO₂ can also be used as a third componentinstead of Li₂ SiO₃. Since Li₂ O is a very unstable compound anddecomposes readily during the sintering process, it is liable to scatteror diffuse into the atmosphere, leaving few Li atoms in the manufacturedsintered body. Moreover, it was confirmed that migration of partiallyionized Li⁺¹ ion under the load of high temperature and high voltageentails degradation of capacitor characteristics. The effects of addedLi ion is provided advantageously by adding the ion in the form of acompound of Li and SiO₂.

Thus, Li ion should be added to the material in the form of a compoundof Li₂ SiO₃.

Example 9

Next, an example where LiAlO₂ is added as a third component will bedescribed. A laminated ceramic capacitor with varistor function wasmanufactured by using similar methods described in Examples 1 to 4,except that the amount of the added third component, LiAlO₂, wasadjusted and changed variously as described in Examples 6 to 8. A/Bratio of Sr₀.8 Ba₀.2 Ba₀.2 TiO₃ was fixed to 0.97; the relative contentsof the first components was fixed to 0.5% for Nb₂ O₅ and Ta₂ O₅ whilethose of combined second components were fixed to 1.0% for MnO₂ andSiO₂, respectively. The results are listed in Table 31.

                  TABLE 31                                                        ______________________________________                                        Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  Nb.sub.2 O.sub.5 ; 0.5 mol %, Ta.sub.2 O.sub.5 ; 0.5 mol %                    MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %                                  Sample                                    ΔC/                                                                          ΔV/V                     Num-  LiAlO.sub.2                                                                            C      tan δ                                                                        V.sub.0.1mΛ                                                                      ESR  C    (%/                            ber   (mol %)  (nF)   (%)  (V)   α                                                                           (mΩ)                                                                         (%)  °C.)                    ______________________________________                                        *256  0.02     621    1.4  4     17  27   -3.2 -1.2                           257   0.05     620    1.4  4     19  25   -2.7 -1.0                           258   0.2      623    1.4  4     19  25   -2.7 -1.0                           259   1.0      623    1.4  4     19  25   -2.7 -1.0                           260   2.0      620    1.4  4     19  25   -2.7 -1.1                           261   4.0      619    1.9  4     19  25   -2.8 -1.1                           *262  5.0      295    4.1  8      8  42   -4.6 -2.9                           ______________________________________                                         Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

As described in Table 31, the first advantage of adding the thirdcomponent, LiAlO₂, to the ceramic material is, just like the addition ofthird component described in Examples 6 to 8, it improves thecapacitance-temperature rate of change and varistor voltage temperaturecoefficient. Al atoms in added LiAlO₂ work as carriers to diffuse liquidphase of Mn, Si and Ti ternary oxide system homogeneously into grainboundaries, thereby forming distinct interfaces among semiconductivecrystal grains and grain boundaries of high electric resistance.

Second, voltage non-linearity coefficient α increases and equivalentseries resistance (ESR) decreases by adding LiAlO₂, because Al atoms inadded LiAlO₂ are solubilized in a solid state into the crystal lattice,thereby decreasing electric resistance of the crystal grains.

When relative molar content of added NaAlO₂ as a third component is lessthan 0.05%, characteristics of the capacitor are not influenceddesirably by the additive; giving no improvements incapacitance-temperature rate of change and varistor temperaturecoefficient, nor increasing voltage non-linearity coefficient α, and notdecreasing equivalent series resistance (ESR).

On the other hand, when the relative molar content of the additiveexceeds 4.0%, which means it exceeds the saturated solubility in thecrystal lattice, excess LiAlO₂ segregates in the grain boundaries,thereby decreasing electric resistance of grain boundaries and hencedecreasing capacitance and voltage non-linearity coefficient α rapidly,increasing equivalent series resistance (ESR) and decreasing sinteringdensity and mechanical strength of the capacitor.

A mixture of Li₂ O and AlO₂ can also be used as a third componentinstead of LiAlO₂.

However, when a mixture of Li₂ O and AlO₃ is used, since Li₂ O is a veryunstable compound and decomposes readily during sintering process, it isliable to scatter or diffuse into the atmosphere, leaving few Li atomsin the manufactured sintered body. Moreover, it was confirmed thatmigration of partially ionized Li⁺¹ ion under the load of hightemperature and high voltage entails degradation of capacitorcharacteristics. The effects of added Li ion is provided advantageouslyby adding the ion in the form of a compound of LiAlO₂.

It was confirmed that Li ion should be added to the material in the formof a compound of LiAlO₂.

Example 10

Na₂ SiO₃ and Al₂ O₃ are added as third and fourth components,respectively in this example. A laminated ceramic capacitor withvaristor function was manufactured by using similar methods described inExamples 1 to 4, except that the amount of the added fourth component,Al₂ O₃, was variously adjusted and changed. A/B ratio of Sr₀.8 Ba₀.2TiO₃ was fixed to 0.97; the relative molar contents of first componentswere fixed to 0.5% for Nb₂ O₅ and Ta₂ O₅, respectively, while those ofcombined second components were fixed to 1.0% for MnO₂ and SiO₂,respectively. Relative molar content of third material, Na₂ SiO₃, wasalso fixed to 0.5%. The results are listed in Table 32.

                  TABLE 32                                                        ______________________________________                                        Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  Nb.sub.2 O.sub.5 ; 0.5 mol %, Ta.sub.2 O.sub.5 ; 0.5 mol %                    MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %, Na.sub.2 SiO.sub.3 ; 0.5        mol %                                                                         Sample                                    ΔC/                                                                          ΔV/V                     Num-  Al.sub.2 O.sub.3                                                                       C      tan δ                                                                        V.sub.0.1mΛ                                                                      ESR  C    (%/                            ber   (mol %)  (nF)   (%)  (V)   α                                                                           (mΩ)                                                                         (%)  °C.)                    ______________________________________                                        *263  0.02     711    1.0  4     18  24   -2.8 -0.8                           264   0.5      710    1.0  4     20  22   -2.3 -0.5                           265   0.1      709    1.0  4     20  22   -2.3 -0.5                           266   0.5      711    1.0  4     20  22   -2.3 -0.5                           267   1.0      711    1.0  4     20  22   -2.3 -0.5                           268   2.0      707    1.5  4     20  22   -2.4 -0.5                           *269  3.0      341    3.5  8      9  38   -3.8 -1.8                           ______________________________________                                         Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

As described in Table 32, the addition of the fourth component, Al₂ O₃,increases voltage non-linearity coefficient α and decreases equivalentseries resistance (ESR), because Al₂ O₃ added is solubilized in a solidstate into the crystal lattice and decreases electric resistance of thecrystal grains. When relative molar content of the fourth componentadded, Al₂ O₃, is less than 0.05%, characteristics of the capacitor arenot influenced desirably by the additive; giving no improvements involtage non-linearity coefficient α and not decreasing equivalent seriesresistance (ESR). On the other hand, when the relative molar content ofthe additive exceeds 2.0%, which means it exceeds the saturatedsolubility in the crystal lattice, excess Al₂ O₃ segregates in the grainboundaries, thereby decreasing electric resistance of grain boundariesand hence decreasing capacitance and voltage non-linearity coefficient αrapidly.

Example 11

Li₂ SiO₃ and Al₂ O₃ are added as third and fourth components,respectively, in this example. A laminated ceramic capacitor withvaristor function was manufactured by using similar methods described inExamples 1 to 4, except that the amount of added fourth component, Al₂O₃, was adjusted and changed variously. A/B ratio of Sr₀.8 Ba₀.2 TiO₃was fixed to 0.97; the relative molar contents of the first componentswas fixed to 0.5% for Nb₂ O₅ and Ta₂ O₅, respectively, while those ofcombined second components were fixed to 1.0% for MnO₂ and SiO₂,respectively. Relative molar content of third material, Li₂ SiO₃, wasalso fixed to 0.5%. The results are listed in Table 33.

                  TABLE 33                                                        ______________________________________                                        Sr.sub.0.8 Ba.sub.0.2 TiO.sub.3 (A/B = 0.97)                                  Nb.sub.2 O.sub.5 ; 0.5 mol %, Ta.sub.2 O.sub.5 ; 0.5 mol %                    MnO.sub.2 ; 1.0 mol %, SiO.sub.2 ; 1.0 mol %, Li.sub.2 SiO.sub.3 ; 0.5        mol %                                                                         Sample                                    ΔC/                                                                          ΔV/V                     Num-  Al.sub.2 O.sub.3                                                                       C      tan δ                                                                        V.sub.0.1mΛ                                                                      ESR  C    (%/                            ber   (mol %)  (nF)   (%)  (V)   α                                                                           (mΩ)                                                                         (%)  °C.)                    ______________________________________                                        *270  0.02     700    1.2  4     18  27   -3.0 -1.0                           271   0.05     699    1.2  4     20  23   -2.4 -0.7                           272   0.1      697    1.2  4     20  22   -2.4 -0.7                           273   0.5      701    1.3  4     20  22   -2.4 -0.6                           274   1.0      700    1.3  4     20  22   -2.4 -0.7                           275   2.0      697    1.8  4     19  24   -2.6 -0.7                           *276  3.0      332    3.8  8      8  33   -3.0 -2.0                           ______________________________________                                         Those marked by the symbol * in the tables are listed for comparison and      not included in the range of claims in the present invention.            

As described in Table 33, addition of the fourth component, Al₂ O₃,increases voltage non-linearity coefficient α and decreases equivalentseries resistance (ESR), because Al₂ O₃ added is solubilized in solidstate into the crystal lattice and decreases electric resistance ofcrystal grains. When relative molar content of fourth component added,Al₂ O₃, is less than 0.05%, characteristics of the capacitor are notinfluenced desirably by the additive; giving no improvements in voltagenon-linearity coefficient α and not decreasing equivalent seriesresistance (ESR). 0n the other hand, when relative molar content of theadditive exceeds 2.0%, which means the saturated solubility in thecrystal lattice, excess Al₂ O₃ segregate in the grain boundaries,thereby decreasing electric resistance of grain boundaries and hencedecreasing capacitance and voltage non-linearity coefficient α rapidly.

Effects of adding one of the third components, Na₂ SiO₃, NaAlO₂, Li₂SiO₃ and LiAlO₂ to the ceramic material were described in Examples 6 to9. In Examples 11 and 12, two combinations of the additives, Na₂ SiO₃ asa third component and Al₂ O₃ as a fourth component; and Li₂ SiO₃ as athird component and Al₂ O₃ as a fourth component were described.However, other combinations can be used with respect to the presentinvention.

One of them is to use only Al₂ O₃ as a third component. In this case, asdescribed in Examples 10 and 11, by adding a relative molar content of0.05 to 2.0% of the third component, Al₂ O₃, voltage non-linearitycoefficient α is improved and equivalent series resistance (ESR) isdecreased. In addition, various combinations of third and fourthcomponents other than those described in Examples 11 and 12, for examplecombination of Na₂ SiO₃ and Li₂ SiO₃ or NaAlO₂ and LiAlO₂, were alsodevised. Improvements in characteristics of the capacitors by adding Na₂SiO₃, Li₂ SiO₃ and Al₂ O₃ as third, fourth and fifth components areconsidered to be possible. In summary, any combinations of theaforementioned compounds are possible as third, fourth, and fifthcomponents, and so on so as to obtain a capacitor of the desiredcharacteristics.

The material of the inner and outer electrodes described in Examples 1to 5 are also applied to the electrodes for the capacitors described inExamples 6 to 10.

Industrial applicability

As described above, according to the present invention, a laminatedceramic capacitor with varistor function is obtained comprising bothfunctions of a capacitor and a varistor, and the capacitor is capable ofmounting on the circuit board. The capacitor works as an ordinarycapacitor which absorbs low voltage noises and high frequency noiseswhile it functions as a varistor when high voltage pulses andelectrostatic charges invade, thereby protecting semiconductors andelectronic instruments from abnormal voltages such as noises, pulses andelectrostatic charges generated by surrounding electronic instruments.The characteristics of the capacitor are always stable to temperaturechanges. Practical applications of the above capacitor are;

(1) The capacitor can replace conventional film, laminated ceramic andsemiconductor type capacitors which are used for by-pass capacitors forprotecting IC and LSI mounted on the circuit cards of electronicequipment.

(2) The capacitor can replace ZnO type capacitors which are used forpreventing malfunctioning of electronic equipment and absorbing ON-OFFsurge arising from inductive loads.

The capacitor possesses both functions described in above-discussedterms of (1) and (2) and wide range of applications are to be expected.

Manufacturing of a laminated ceramic capacitor with varistor function ofthe present invention is made easy because simultaneous sintering of thematerials of ceramic capacitor with varistor function with the materialsof inner electrode has became possible for the following reasons Besidesmaterials to be semiconductive are added to Sr.sub.(1-x) Ba_(x) TiO₃with excess Ti, Mn-Si components composed of MnO₂ and SiO₂ is also addedin the sintering process. Grain boundary insulated structure ofsemiconductor type ceramic capacitor is formed readily by a re-oxidationprocess by using the material of the above-described composition,whereas surface diffusion process of metal oxides is necessary in themanufacturing process of conventional ceramic capacitor. Many troublesof breaking the electrical connection in inner electrodes,de-lamination, cracks in ceramic sheets, decrease in sintering densityand non-uniformity of the texture in the sintered body in the laminatedceramic capacitor with varistor function manufactured are prevented fromoccurring by sintering the raw laminated body in the air. Electriccharacteristics such as capacitance, voltage non-linearity coefficient αand varistor voltage, and reliability of the products are largelyimproved. The present invention provides two major advantages in theaforementioned composition of the starting materials and in themanufacturing process of the capacitors.

Since the laminated ceramic capacitor with varistor function of thepresent invention is smaller in size and possesses larger capacitanceand higher performances compared to conventional single plate typeceramic capacitor with varistor function, the former capacitor isexpected to have a wide range of applications as highly integratedmounting elements for electronic equipment such as video camera andcommunication apparatus.

Therefore, according to the present invention capacitor elementscomprising the functions of protecting semiconductors and electronicequipment from invading abnormal voltages such as noises, pulses andelectrostatic charges can be obtained. Characteristics of the capacitoris so stable to temperature changes that effects of the presentinvention are greatly improved from the point of practical applications.

We claim:
 1. A semiconductor-type laminated ceramic capacitor with agrain boundary-insulated structure comprising a plurality of innerelectrodes on the surface of the grain boundary insulated, semiconductortype ceramic sheets, the terminal of each of said inner electrodes beingextended to one edge of the corresponding ceramic sheet and said ceramicsheets being laminated so that said terminals of said inner electrodescome to the corresponding opposite edges of said ceramic sheetsalternatively one by one; and outer electrodes electrically connected tosaid terminals of inner electrodes at opposite edges of each of saidgrain boundary insulated, semiconductor type ceramic sheets, whereinsaid ceramic sheets comprise of a material of the composition ofSr.sub.(1-x) Ba_(x) TiO₃ containing excess Ti to make final molecularratio of Ti to Sr.sub.(1-x) Ba_(x) in the range of 0.95≦Sr.sub.(1-x)Ba_(x) /Ti<1.00 (where x is in the range of 0<x<0.3); at least one ormore kinds of the compounds selected from Nb₂ O₅, Ta₂ O₅, V₂ O₅, W₂ O₅,Dy₂ O.sub. 3, Nd₂ O₃, Y₂ O₃, La₂ O₃ or CeO₂ are added to said ceramicmaterial to make their relative molar content in the range from 0.05 to2.0%; and Mn and Si are also included in said ceramic material to theamount of their combined relative molar content, converting into MnO₂and SiO₂ respectively, in the range of 0.2 to 5.0%.
 2. Asemiconductor-type laminated ceramic capacitor with a grainboundary-insulated structure according to claim 1, wherein said innerelectrode is made of at least one or more kinds of metals selected fromAu, Pt, Rh, Pd or Ni, or alloys or compositions thereof.
 3. Asemiconductor-type laminated ceramic capacitor with a grainboundary-insulated structure according to claim 1, wherein said outerelectrode is made of at least one or more kinds of metals selected fromPd, Ag, Ni, Cu or Zn, or alloys or compositions thereof.
 4. Asemiconductor-type laminated ceramic capacitor with a grainboundary-insulated structure comprising a plurality of inner electrodeson the surface of the grain boundary insulated, semiconductor typeceramic sheets, the terminal of each of said inner electrodes beingextended to one edge of the corresponding ceramic sheet and said ceramicsheets being laminated so that said terminals of said inner electrodescome to the corresponding opposite edges of said ceramic sheetsalternatively one by one; and outer electrodes electrically connected tosaid terminals of inner electrodes at opposite edges of each of saidgrain boundary insulated, semiconductor type ceramic sheets, whereinsaid ceramic sheets comprise of a material of the composition ofSr.sub.(1-x) Ba_(x) TiO₃ containing excess Ti to make final molecularratio of Ti to Sr.sub.(1-x) Ba_(x) in the range of 0.95≦Sr.sub.(1-x)Ba_(x) /Ti<1.00 (where x is in the range of 0<x≦0.3); at least one ormore kinds of the compounds selected from Nb₂ O₅, Ta₂ O₅, V₂ O₅, W₂ O₅,Dy₂ O₃, Nd₂ O₃, Y₂ O₃, La₂ O₃ or CeO₂ are added to said ceramic materialto make their relative molar content in the range from 0.05 to 2.0%; Mnand Si are also included in said ceramic material to the amount of theircombined relative molar content, converting into MnO₂ and SiO₂respectively, in the range of 0.2 to 5.0%; and Na₂ SiO₃ is furtherincluded in said ceramic material to make relative molar content in therange of 0.05-2.0%.
 5. A semiconductor-type laminated ceramic capacitorwith a grain boundary-insulated structure comprising a plurality ofinner electrodes on the surface of the grain boundary insulated,semiconductor type ceramic sheets, the terminal of each of said innerelectrodes being extended to one edge of the corresponding ceramic sheetand said ceramic sheets being laminated so that said terminals of saidinner electrodes come to the corresponding opposite edges of saidceramic sheets alternatively one by one; and outer electrodeselectrically connected to said terminals of inner electrodes at oppositeedges of each of said grain boundary insulated, semiconductor typeceramic sheets, wherein said ceramic sheets comprise of a material ofthe composition of Sr.sub.(1-x) Ba_(x) TiO₃ (where 0.001≦x≦0.3)containing excess Ti to make final molecular ratio of Ti to Sr.sub.(1-x)Ba_(x) in the range of 0.95≦Sr.sub.(1-x) Ba_(x) /Ti<1.00 (where x is inthe range of 0<x≦0.3); at least one or more kinds of the compoundsselected from Nb₂ O₅, Ta₂ O₅, V₂ O₅, W₂ O₅, Dy₂ O₃, Nd₂ O₃, Y₂ O₃, La₂O₃ or CeO₂ are added to said ceramic material to make their relativemolar content in the range from 0.05 to 2.0%; Mn and Si are alsoincluded in said ceramic material to the amount of their combinedrelative molar content, converting into MnO₂ and SiO₂ respectively, inthe range of 0.2 to 5.0%; and NaAlO₂ is further included in said ceramicmaterial to make relative molar content in the range of 0.05-4.0%.
 6. Asemiconductor-type laminated ceramic capacitor with a grainboundary-insulated structure comprising a plurality of inner electrodeson the surface of the grain boundary insulated, semiconductor typeceramic sheets, the terminal of each of said inner electrodes beingextended to one edge of the corresponding ceramic sheet and said ceramicsheets being laminated so that said terminals of said inner electrodescome to the corresponding opposite edges of said ceramic sheetsalternatively one by one; and outer electrodes electrically connected tosaid terminals of inner electrodes at opposite edges of each of saidgrain boundary insulated, semiconductor type ceramic sheets, whereinsaid ceramic sheets comprise of a material of the composition ofSr.sub.(1-x) Ba_(x) TiO₃ containing excess Ti to make final molecularratio of Ti to Sr.sub.(1-x) Ba_(x) in the range of 0.95≦Sr.sub.(1-x)Ba_(x) /Ti<1.00 at least one or more kinds of the compounds selectedfrom Nb₂ O₅, Ta₂ O₅, V₂ O₅, W₂ O₅, Dy₂ O₃, Nd₂ O₃, Y₂ O₃, La₂ O₃ or CeO₂are added to said ceramic material to make their relative molar contentin the range from 0.05 to 2.0%; Mn and Si are also included in saidceramic material to the amount of their combined relative molar content,converting into MnO₂ and SiO₂ respectively, in the range of 0.2 to 5.0%;and Li₂ SiO₃ is further included in said ceramic material to makerelative molar content in the range of 0.05-2.0%.
 7. Asemiconductor-type laminated ceramic capacitor with a grainboundary-insulated structure comprising a plurality of inner electrodeson the surface of the grain boundary insulated, semiconductor typeceramic sheets, the terminal of each of said inner electrodes beingextended to one edge of the corresponding ceramic sheet and said ceramicsheets being laminated so that said terminals of said inner electrodescome to the corresponding opposite edges of said ceramic sheetsalternatively one by one; and outer electrodes electrically connected tosaid terminals of inner electrodes at opposite edges of each of saidgrain boundary insulated, semiconductor type ceramic sheets, wherein:said ceramic sheets comprise of a material of the composition ofSr.sub.(1-x) Ba_(x) TiO₃ containing excess Ti to make final molecularratio of Ti to Sr.sub.(1-x) Ba_(x) in the range of 0.95≦Sr.sub.(1-x)Ba_(x) /Ti<1.00 (where x is in the range of 0<x≦0.3); at least one ormore kinds of the compounds selected from Nb₂ O₅, Ta₂ O₅, V₂ O₅, W₂ O₅,Dy₂ O.sub. 3, Nd₂ O₃, Y₂ O₃, La₂ O₃ or CeO₂ are added to said ceramicmaterial to make their relative molar content in the range from 0.05 to2.0%; Mn and Si are also included in said ceramic material to the amountof their combined relative molar content, converting into MnO₂ and SiO₂respectively, in the range of 0.2 to 5.0%; and Li₂ AlO₂ is furtherincluded in said ceramic material to make relative molar content in therange of 0.05-4.0%.
 8. A semiconductor-type laminated ceramic capacitorwith a grain boundary-insulated structure comprising a plurality ofinner electrodes on the surface of the grain boundary insulated,semiconductor type ceramic sheets, the terminal of each of said innerelectrodes being extended to one edge of the corresponding ceramic sheetand said ceramic sheets being laminated so that said terminals of saidinner electrodes come to the corresponding opposite edges of saidceramic sheets alternatively one by one; and outer electrodeselectrically connected to said terminals of inner electrodes at oppositeedges of each of said grain boundary insulated, semiconductor typeceramic sheets, wherein: said ceramic sheets comprise of a material ofthe composition of Sr.sub.(1-x) Ba_(x) TiO₃ containing excess Ti to makefinal molecular ratio of Ti to Sr.sub.(1-x) Ba_(x) in the range of0.95≦Sr.sub.(1-x) Ba_(x) /Ti<1.00 (where x is in the range of 0<x≦0.3);at least one or more kinds of the compounds selected from Nb₂ O₅, Ta₂O₅, V₂ O₅, W₂ O₅, Dy₂ O.sub. 3, Nd₂ O₃, Y₂ O₃, La₂ O₃ or CeO₂ are addedto said ceramic material to make their relative molar content in therange from 0.05 to 2.0%; Mn and Si are also included in said ceramicmaterial to the amount of their combined relative molar content,converting into MnO₂ and SiO₂ respectively, in the range of 0.2 to 5.0%,and Na₂ SiO₃ and Al₂ O₃ are further included in said ceramic material tomake relative molar content in the range of 0.05-2.0% and 0.05-2.0%,respectively.
 9. A semiconductor-type laminated ceramic capacitor with agrain boundary-insulated structure comprising a plurality of innerelectrodes on the surface of the grain boundary insulated, semiconductortype ceramic sheets, the terminal of each of said inner electrodes beingextended to one edge of the corresponding ceramic sheet and said ceramicsheets being laminated so that said terminals of said inner electrodescome to the corresponding opposite edges of said ceramic sheetsalternatively one by one; and outer electrodes electrically connected tosaid terminals of inner electrodes at opposite edges of each of saidgrain boundary insulated, semiconductor type ceramic sheets, wherein:said ceramic sheets comprise of a material of the composition ofSr.sub.(1-x) Ba_(x) TiO₃ containing excess Ti to make final molecularratio of Ti to Sr.sub.(1-x) Ba_(x) in the range of 0.95≦Sr.sub.(1-x)Ba_(x) /Ti<1.00 (where x is in the range of 0<x≦0.3); at least one ormore kinds of the compounds selected from Nb₂ O₅, Ta₂ O₅, V₂ O₅, W₂ O₅,Dy₂ O₃, Nd₂ O₃, Y₂ O₃, La₂ O₃ or CeO₂ are added to said ceramic materialto make their relative molar content in the range from 0.05 to 2.0%; Mnand Si are also included in said ceramic material to the amount of theircombined relative molar content, converting into MnO₂ and SiO₂respectively, in the range of 0.2 to 5.0%; and Li₂ SiO₃ and Al₂ O₃ arefurther included in said ceramic material to make their relative molarcontents in the range of 0.05-2.0% and 0.05-2.0%, respectively.
 10. Asemiconductor-type laminated ceramic capacitor with a grainboundary-insulated structure according to claim 2, wherein said outerelectrode is made of at least one or more kinds of metals selected fromPd, Ag, Ni, Cu or Zn, or alloys or compositions thereof.